Synonyms
More meanings
Tip: select a single word for meaning & synonyms.
Select multiple words normally to copy text.
Magnetic Effects of Electric Current: Class 10 Science answers
Get summaries, questions, answers, solutions, notes, extras, PDF and guides for Chapter 12 Magnetic Effects of Electric Current: Class 10 Science textbook, which is part of the syllabus for students studying under SEBA (Assam Board), NBSE (Nagaland Board), TBSE (Tripura Board), CBSE (Central Board), MBOSE (Meghalaya Board), BSEM (Manipur Board), WBBSE (West Bengal Board), and all other boards following the NCERT books. These solutions, however, should only be treated as references and can be modified/changed.
If you notice any errors in the notes, please mention them in the comments
Summary
Electric current can do more than just create heat. A wire that carries electricity also behaves like a magnet. A scientist named Hans Christian Oersted discovered this when he noticed a compass needle moving near an electric wire. This showed that electricity and magnetism are linked. This important link is used in many devices we use, such as radios and televisions.
A magnet has an area around it where its magnetic force can be felt. This area is called a magnetic field. We can imagine this field by looking at how iron filings arrange themselves around a magnet, forming patterns of lines. These are known as magnetic field lines. These lines show the direction and strength of the magnetic field. By agreement, field lines are shown coming out of a magnet’s north pole and going into its south pole. Inside the magnet, they travel from the south pole back to the north pole, making them complete, closed loops. An important property of these lines is that they never cross each other. If they did, it would mean a compass at that point would try to point in two directions at once, which is impossible.
When electricity flows through a straight wire, it creates a magnetic field in the form of circles around the wire. A simple way to find the direction of this field is the “Right-Hand Thumb Rule.” If you imagine holding the wire with your right hand, with your thumb pointing in the direction of the electric current, the way your fingers curl around the wire shows the direction of the magnetic field. The magnetic field becomes stronger if the current increases or if you are closer to the wire. If this wire is bent into a circular loop, the magnetic field lines inside the loop all point in the same direction. A coil made of many such loops, called a solenoid, acts very much like a bar magnet when electricity passes through it. The magnetic field inside a solenoid is strong and uniform. An electromagnet is made by placing a piece of material like soft iron inside a current-carrying solenoid.
If a wire carrying an electric current is placed within the magnetic field of another magnet, the wire will experience a force. This force can cause the wire to move. The direction of this movement depends on the direction of the current in the wire and the direction of the magnetic field. “Fleming’s Left-Hand Rule” is a way to determine the direction of this force. If you stretch the first finger, second finger, and thumb of your left hand so they are at right angles to each other, and your first finger points in the direction of the magnetic field, and your second finger points in the direction of the current, then your thumb will point in the direction of the force or motion. This principle is used in electric motors.
In our homes, the electricity we use is supplied through wires. Typically, there is a ‘live’ wire, often with red insulation, and a ‘neutral’ wire, often with black insulation. For safety, there is also an ‘earth’ wire, usually with green insulation. This earth wire is connected to the metal casings of appliances. If a fault causes the live wire to touch the metal casing, the earth wire provides a safe path for the current to flow to the ground, preventing electric shocks. Fuses are another vital safety feature in circuits. If too much current flows, for example, due to a ‘short circuit’ where the live and neutral wires accidentally touch, the thin wire inside the fuse melts and breaks the circuit. This stops the flow of excessive current, protecting appliances from damage and reducing the risk of fire.
Textbook solutions
Intext Questions and Answers I
1. Why does a compass needle get deflected when brought near a bar magnet?
Answer: A compass needle gets deflected when brought near a bar magnet because the compass needle is, in fact, a small bar magnet. The bar magnet exerts a magnetic force on the compass needle. This interaction occurs because like magnetic poles repel each other, while unlike poles of magnets attract each other, causing the compass needle to deflect.
Intext Questions and Answers II
1. Draw magnetic field lines around a bar magnet.
Answer:
2. List the properties of magnetic field lines.
Answer: The properties of magnetic field lines are:
(i) The direction of the magnetic field is taken to be the direction in which a north pole of the compass needle moves inside it.
(ii) By convention, field lines emerge from the north pole and merge at the south pole.
(iii) Inside the magnet, the direction of field lines is from its south pole to its north pole.
(iv) Magnetic field lines are closed curves.
(v) The relative strength of the magnetic field is shown by the degree of closeness of the field lines. The field is stronger where the field lines are crowded.
(vi) No two field-lines are found to cross each other.
3. Why don’t two magnetic field lines intersect each other?
Answer: Two magnetic field lines don’t intersect each other because if they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.
Intext Questions and Answers III
1. Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Answer: To find out the direction of the magnetic field inside and outside the circular loop of wire, the right-hand rule is applied. Imagine that you are holding a current-carrying straight conductor, which can be considered as a segment of the loop, in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field. For the circular loop of wire lying in the plane of the table with the current passing through it clockwise, by applying the right-hand rule, it is easy to check that every section of the wire contributes to the magnetic field lines in the same direction within the loop. The direction of the magnetic field inside the loop is directed into the plane of the table, and outside the loop, the magnetic field is directed out of the plane of the table.
2. The magnetic field in a given region is uniform. Draw a diagram to represent it.
Answer:
3. Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(a) is zero.
(b) decreases as we move towards its end.
(c) increases as we move towards its end.
(d) is the same at all points.
Answer: The correct option is (d).
Explanation: The magnetic field inside a long straight solenoid-carrying current is the same at all points. The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.
Intext Questions and Answers IV
1. Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)
(a) mass
(b) speed
(c) velocity
(d) momentum
Answer: (c) velocity and (d) momentum.
Explanation:
As explained by Fleming’s left-hand rule (page 9), the magnetic force on a moving charged particle is always perpendicular to its direction of motion.
- A force perpendicular to the motion changes the particle’s direction but does not change its speed.
- Velocity is a vector that includes both speed and direction. Since the direction changes, the velocity changes.
- Momentum is also a vector (mass × velocity). Since the velocity changes, the momentum also changes.
- The proton’s mass and speed remain constant.
2. In Activity 12.7, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?
Answer: The displacement of the rod AB will increase in all three cases.
Explanation: Activity 12.7 demonstrates that a current-carrying conductor in a magnetic field experiences a force, which causes displacement. The magnitude of this force is directly proportional to:
- (i) The current (I) in the conductor.
- (ii) The strength of the magnetic field (B).
- (iii) The length (L) of the conductor within the magnetic field.
Therefore, increasing the current, using a stronger magnet, or increasing the length of the rod will all result in a larger force, and consequently, a greater displacement.
3. A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south
(b) towards east
(c) downward
(d) upward
Answer: (d) upward
Explanation: This can be determined using Fleming’s Left-Hand Rule (page 9):
- Current (Middle Finger): The particle is positively charged and moving west, so the conventional current is towards the west.
- Force (Thumb): The particle is deflected towards the north.
- Magnetic Field (Forefinger): When you align your left hand with your thumb pointing north and your middle finger pointing west, your forefinger points upward.
Intext Questions and Answers V
1. Name two safety measures commonly used in electric circuits and appliances.
Answer: Two safety measures commonly used in electric circuits and appliances are the earth wire and the electric fuse. The earth wire, which has insulation of green colour, is usually connected to a metal plate deep in the earth near the house; this is used as a safety measure, especially for those appliances that have a metallic body, to ensure that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shock. An electric fuse is an important component of all domestic circuits that prevents damage to the appliances and the circuit due to overloading by stopping the flow of unduly high electric current; the Joule heating that takes place in the fuse melts it to break the electric circuit.
2. An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
Answer: For an electric oven of 2 kW power rating operated in a domestic electric circuit of 220 V, the current it will draw is calculated as Power (P) / Voltage (V), which is 2000 W / 220 V, approximately 9.09 A. Since this current of 9.09 A is higher than the circuit’s current rating of 5 A, the circuit will experience overloading. In such a situation, where the current in the circuit abruptly increases to an unduly high value, the electric fuse is designed to protect the circuit and appliance. The Joule heating that takes place in the fuse, due to this unduly high electric current, will melt the fuse, thereby breaking the electric circuit. This prevents possible damage to the electric oven and the household wiring.
3. What precaution should be taken to avoid the overloading of domestic electric circuits?
Answer: A precaution that should be taken to avoid the overloading of domestic electric circuits is to avoid connecting too many appliances to a single socket, as sometimes overloading is caused by this.
Exercise Questions and Answers
1. Which of the following correctly describes the magnetic field near a long straight wire?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.
Answer: (d) The field consists of concentric circles centred on the wire.
2. At the time of short circuit, the current in the circuit
(a) reduces substantially.
(b) does not change.
(c) increases heavily.
(d) vary continuously.
Answer: (c) increases heavily.
3. State whether the following statements are true or false.
(a) The field at the centre of a long circular coil carrying current will be parallel straight lines.
Answer: True.
(b) A wire with a green insulation is usually the live wire of an electric supply.
Answer: False.
4. List two methods of producing magnetic fields.
Answer: Two methods of producing magnetic fields are:
(i) Using a magnet, as a magnetic field exists in the region surrounding a magnet.
(ii) Passing an electric current through a metallic wire, as a metallic wire carrying an electric current has associated with it a magnetic field.
5. When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
Answer: The force experienced by a current-carrying conductor placed in a magnetic field is largest (or the magnitude of the force is the highest) when the direction of current is at right angles to the direction of the magnetic field.
6. Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
Answer: The direction of current is taken opposite to the direction of motion of electrons. Thus, the current is from the front wall towards the back wall. The deflection (force) is to the right side. Applying Fleming’s left-hand rule, where the first finger points in the direction of the magnetic field, the second finger in the direction of current, and the thumb points in the direction of motion or force, the direction of the magnetic field is vertically downwards.
7. State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current, (ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (iii) current induced in a coil due to its rotation in a magnetic field.
Answer: (i) The rule is the Right-Hand Thumb Rule.
Reason: Imagine you are holding a current-carrying straight conductor in your right hand such that your thumb points in the direction of the current. The direction in which your fingers wrap around the conductor gives the direction of the magnetic field lines.
(ii) The rule is Fleming’s Left-Hand Rule.
Reason: Stretch the thumb, forefinger, and middle finger of your left hand so that they are mutually perpendicular. If the forefinger points in the direction of the magnetic field and the middle finger points in the direction of the current, then the thumb will point in the direction of the force (or motion) experienced by the conductor.
(iii) The rule is Fleming’s Right-Hand Rule.
Reason: Stretch the thumb, forefinger, and middle finger of your right hand so they are mutually perpendicular. If the thumb points in the direction of the motion of the conductor, and the forefinger points in the direction of the magnetic field, then the middle finger will point in the direction of the induced current.
8. When does an electric short circuit occur?
Answer: An electric short circuit occurs when the live wire and the neutral wire come into direct contact. This can happen when the insulation of wires is damaged or there is a fault in the appliance. In such a situation, the current in the circuit abruptly increases.
9. What is the function of an earth wire? Why is it necessary to earth metallic appliances?
Answer: The function of an earth wire is to serve as a safety measure, especially for those appliances that have a metallic body. The earth wire, which has insulation of green colour, is usually connected to a metal plate deep in the earth near the house. The metallic body of the appliance is connected to the earth wire, which provides a low-resistance conducting path for the current.
It is necessary to earth metallic appliances because it ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth. This prevents the user from getting a severe electric shock.
Extras
Additional MCQs (Knowledge Based)
1. The direction of magnetic field lines inside a bar magnet is from its _____________ pole to its _____________ pole.
A. North, South
B. South, North
C. East, West
D. West, East
Answer: B. South, North
2. A student lists observations about magnetic fields. Which statement is incorrect?
A. Iron filings align along magnetic field lines.
B. Magnetic field lines can cross each other.
C. A compass needle is a small bar magnet.
D. Field lines are crowded where the field is strong.
Answer: B. Magnetic field lines can cross each other.
3. The Right-Hand Thumb Rule helps determine the direction of the magnetic field around a current-carrying conductor, similar to how Fleming’s Left-Hand Rule helps determine the _____________ acting on a conductor in a magnetic field.
A. Current
B. Voltage
C. Force
D. Resistance
Answer: C. Force
4. Under which condition is the force experienced by a current-carrying conductor placed in a magnetic field the greatest?
A. When the current is parallel to the field.
B. When the current is at 45° to the field.
C. When the current is perpendicular to the field.
D. When the conductor is very short.
Answer: C. When the current is perpendicular to the field.
5. Who discovered that a compass needle deflects when an electric current passes through a nearby metallic wire?
A. Andre Marie Ampere
B. Michael Faraday
C. Hans Christian Oersted
D. James Clerk Maxwell
Answer: C. Hans Christian Oersted
6. Identify the item that is NOT primarily a safety device in domestic electrical circuits.
A. Electric fuse
B. Earth wire
C. Main switch
D. Insulated wires
Answer: C. Main switch
7. Which of the following statements correctly describe magnetic field lines?
P. They emerge from the north pole of a magnet.
Q. They form closed and continuous curves.
R. Inside a magnet, they go from north to south.
S. Their density indicates the field’s strength.
A. P, Q, and S
B. Q, R, and S
C. P, R, and S
D. P, Q, and R
Answer: A. P, Q, and S
8. Which statement is NOT true about the magnetic field inside a long, current-carrying solenoid?
A. The field lines are nearly parallel.
B. The magnetic field is uniform.
C. The field strength is zero at the axis.
D. It resembles the field of a bar magnet overall.
Answer: C. The field strength is zero at the axis.
9. The region surrounding a magnet in which the force of the magnet can be detected is known as its _____________ .
A. Electric field
B. Magnetic field
C. Gravitational field
D. Force zone
Answer: B. Magnetic field
10. If the current in a straight conductor is flowing vertically downwards, the magnetic field lines will be concentric circles in which direction when viewed from above?
A. Clockwise
B. Anticlockwise
C. Radially outwards
D. Radially inwards
Answer: A. Clockwise
11. What is the conventional direction of magnetic field lines outside a bar magnet?
A. From South pole to North pole
B. From North pole to South pole
C. From the center outwards
D. Along the length only
Answer: B. From North pole to South pole
12. An electric current flowing through a metallic conductor produces a _____________ around it.
A. Heating effect only
B. Magnetic effect
C. Chemical effect
D. Sound effect
Answer: B. Magnetic effect
13. The strength of the magnetic field produced by a current-carrying straight wire increases if the _____________ .
A. Length of the wire increases
B. Current in the wire increases
C. Wire material is changed
D. Surrounding temperature drops
Answer: B. Current in the wire increases
14. A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a _____________ .
A. Resistor
B. Capacitor
C. Solenoid
D. Inductor
Answer: C. Solenoid
15. In Fleming’s Left-Hand Rule, if the forefinger points in the direction of the magnetic field and the middle finger points in the direction of the current, then the thumb points in the direction of the _____________ .
A. Voltage
B. Resistance
C. Motion or force
D. Electric field
Answer: C. Motion or force
16. The potential difference between the live wire and the neutral wire in domestic electric supply in India is typically _____________ .
A. 110 V
B. 220 V
C. 50 V
D. 12 V
Answer: B. 220 V
17. What is the usual color of the insulation for the earth wire in a domestic electrical circuit?
A. Red
B. Black
C. Green
D. Blue
Answer: C. Green
18. The phenomenon that occurs when the live wire and the neutral wire come into direct contact, causing a sudden surge in current, is known as _____________ .
A. Overloading
B. Earthing
C. Short-circuiting
D. Open circuit
Answer: C. Short-circuiting
19. Which property of a proton is most likely to change when it moves freely in a magnetic field (not parallel to it)?
A. Mass
B. Charge
C. Speed
D. Velocity
Answer: D. Velocity
20. An electromagnet is typically made by placing a core of _____________ inside a current-carrying coil.
A. Copper
B. Soft iron
C. Aluminium
D. Steel
Answer: B. Soft iron
21. The frequency of AC (alternating current) power supplied to homes in India is generally _____________ .
A. 60 Hz
B. 50 Hz
C. 100 Hz
D. 25 Hz
Answer: B. 50 Hz
22. What happens to the magnetic field strength as one moves away from a straight current-carrying conductor?
A. It increases
B. It decreases
C. It remains constant
D. It becomes zero instantly
Answer: B. It decreases
23. The unit of magnetic field strength, named in honor of the scientist who discovered the magnetic effect of current, is the _____________ .
A. Volt
B. Ampere
C. Oersted
D. Watt
Answer: C. Oersted
24. In domestic wiring, appliances are connected in _____________ so that each gets the same potential difference.
A. Series
B. Parallel
C. A mixed combination
D. A star configuration
Answer: B. Parallel
25. The primary purpose of an electric fuse in a circuit is to protect appliances from damage due to _____________ .
A. Low voltage
B. High resistance
C. Overloading
D. Power factor changes
Answer: C. Overloading
Additional MCQs (Competency Based)
1. Assertion (A): When an electric current passes through a metallic wire placed nearby a compass, the compass needle gets deflected.
Reason (R): An electric current-carrying wire behaves like a magnet.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (a) Both A and R are true and R is the correct explanation of A.
2. Assertion (A): Magnetic field lines around a bar magnet never intersect each other.
Reason (R): If two field lines were to intersect, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (a) Both A and R are true and R is the correct explanation of A.
3. Assertion (A): The magnetic field inside a long straight solenoid carrying current is uniform.
Reason (R): The field lines inside the solenoid are in the form of parallel straight lines.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (a) Both A and R are true and R is the correct explanation of A.
4. Assertion (A): In domestic electric circuits, appliances are connected in parallel.
Reason (R): This ensures that each appliance receives a different potential difference depending on its power rating.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (c) A is true but R is false.
5. An electrician is setting up a circuit with a straight copper wire carrying current from North to South. A compass is placed directly above the wire. In which direction will the North pole of the compass needle deflect?
(a) Towards East
(b) Towards West
(c) Towards North
(d) Towards South
Answer: (a) Towards East
6. A student observes that iron filings sprinkled on a cardboard placed over a current-carrying straight wire arrange themselves in concentric circles. If the student increases the current flowing through the wire, what change will be observed in the pattern of iron filings?
(a) The circles will become elliptical.
(b) The filings will arrange in straight lines.
(c) The circles will become more densely packed near the wire.
(d) The direction of the circles will reverse.
Answer: (c) The circles will become more densely packed near the wire.
7. In a household, a new high-power appliance like a geyser is to be installed. Which of the following circuit provisions is most crucial for its safe operation?
(a) Connecting it to a 5A rated circuit.
(b) Ensuring it has a switch with a red indicator.
(c) Connecting its metallic body to the earth wire.
(d) Using a black insulated wire for its live connection.
Answer: (c) Connecting its metallic body to the earth wire.
8. An electron beam is moving horizontally from east to west. It enters a region with a uniform magnetic field pointing vertically upwards. In which direction will the electron beam be deflected?
(a) North
(b) South
(c) Upwards
(d) Downwards
Answer: (a) North
9. Match the rule/phenomenon in Column A with its primary application/description in Column B.
| Column A | Column B |
| (i) Right-Hand Thumb Rule | 1. Direction of force on a current-carrying conductor in a magnetic field |
| (ii) Fleming’s Left-Hand Rule | 2. Pattern of magnetic field lines around a bar magnet |
| (iii) Oersted’s Discovery | 3. Direction of magnetic field around a straight current-carrying wire |
| (iv) Solenoid Principle | 4. Electric current produces a magnetic effect |
(a) (i)-3, (ii)-1, (iii)-4, (iv)-2
(b) (i)-3, (ii)-1, (iii)-2, (iv)-4
(c) (i)-1, (ii)-3, (iii)-4, (iv)-2
(d) (i)-4, (ii)-2, (iii)-1, (iv)-3
Answer: (a) (i)-3, (ii)-1, (iii)-4, (iv)-2
10. Match the component in a domestic circuit (Column A) with its primary characteristic or function (Column B).
| Column A | Column B |
| (i) Live Wire | 1. Safety device, prevents damage from high current |
| (ii) Neutral Wire | 2. Carries current to the appliance, red insulation |
| (iii) Earth Wire | 3. Completes the circuit, black insulation |
| (iv) Fuse | 4. Safety path for leakage current, green insulation |
(a) (i)-2, (ii)-3, (iii)-1, (iv)-4
(b) (i)-2, (ii)-3, (iii)-4, (iv)-1
(c) (i)-3, (ii)-2, (iii)-4, (iv)-1
(d) (i)-1, (ii)-4, (iii)-2, (iv)-3
Answer: (b) (i)-2, (ii)-3, (iii)-4, (iv)-1
11. Arrange the following steps in the correct sequence to demonstrate the magnetic effect of electric current using a straight wire and a compass, starting from setting up the circuit.
(i) Observe the change in the position of the compass needle.
(ii) Place a small compass near the copper wire.
(iii) Take a straight thick copper wire and place it in an electric circuit.
(iv) Pass the current through the circuit by inserting the key.
(a) (iii) → (ii) → (iv) → (i)
(b) (ii) → (iii) → (iv) → (i)
(c) (iii) → (iv) → (ii) → (i)
(d) (iv) → (iii) → (ii) → (i)
Answer: (a) (iii) → (ii) → (iv) → (i)
12. Consider the process of drawing a magnetic field line of a bar magnet using a small compass. Arrange the following actions in the correct sequence.
(i) Join the points marked on the paper by a smooth curve.
(ii) Mark the position of the two ends of the needle.
(iii) Place the compass near one pole of the magnet.
(iv) Move the needle to a new position such that its south pole occupies the position previously occupied by its north pole.
(a) (iii) → (ii) → (iv) → (i)
(b) (ii) → (iii) → (iv) → (i)
(c) (iii) → (iv) → (ii) → (i)
(d) (iv) → (ii) → (iii) → (i)
Answer: (a) (iii) → (ii) → (iv) → (i)
13. “The unit of magnetic field strength is named the oersted in his honor.”
Whose honor is being referred to in this statement?
(a) Andre Marie Ampere
(b) Michael Faraday
(c) Hans Christian Oersted
(d) James Clerk Maxwell
Answer: (c) Hans Christian Oersted
14. “In our country, the potential difference between the live wire and the neutral wire is 220 V. These wires supply electricity to separate circuits within the house. Often, two separate circuits are used, one of 15 A current rating… The other circuit is of 5 A current rating…”
Based on this information, which statement is correct regarding domestic circuits?
(a) All appliances in a house are connected to a single circuit with a 220V supply.
(b) Higher power appliances are typically connected to a 5A rated circuit.
(c) The potential difference supplied to homes is typically 15V or 5V.
(d) Different circuits with specific current ratings are used for different types of appliances.
Answer: (d) Different circuits with specific current ratings are used for different types of appliances.
15. A current-carrying circular coil has ‘N’ turns. Another similar coil has ‘2N’ turns, with the same current flowing through each turn. How does the magnetic field produced at the center of the second coil compare to the first?
(a) It is half as strong.
(b) It is the same.
(c) It is twice as strong.
(d) It is four times as strong.
Answer: (c) It is twice as strong.
16. A straight conductor carries a certain current. The magnetic field is measured at point P, a distance ‘d’ from the wire. If the measurement point is moved to Q, at a distance ‘2d’ from the wire, while the current remains constant, how does the magnetic field strength at Q compare to that at P?
(a) It is doubled.
(b) It is halved.
(c) It remains the same.
(d) It becomes one-fourth.
Answer: (b) It is halved.
17. Assertion (A): An electric fuse is an important safety device in domestic circuits.
Reason (R): A fuse contains a wire that melts and breaks the circuit if the current exceeds a safe limit, preventing damage to appliances.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (a) Both A and R are true and R is the correct explanation of A.
18. Assertion (A): A current-carrying solenoid behaves like a bar magnet.
Reason (R): The magnetic field lines inside a solenoid are circular and non-uniform.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (c) A is true but R is false.
19. A technician is investigating a fault in a household where appliances frequently stop working and the fuse blows. Upon inspection, it is found that the insulation on the live and neutral wires has worn out at a point, causing them to touch. What is this condition called?
(a) Overloading due to high voltage
(b) Earth leakage
(c) Short-circuiting
(d) Open circuit
Answer: (c) Short-circuiting
20. A student is holding a straight current-carrying wire in their right hand such that the thumb points in the direction of the current. What do the fingers wrapped around the wire indicate?
(a) The direction of the electric field.
(b) The direction of the force on the wire.
(c) The direction of the magnetic field lines.
(d) The material of the wire.
Answer: (c) The direction of the magnetic field lines.
21. Match the phenomenon (Column A) with the scientist primarily associated with its discovery or explanation (Column B).
| Column A | Column B |
| (i) Accidental discovery of compass deflection by current | 1. Andre Marie Ampere |
| (ii) Rule for direction of force on current in magnetic field | 2. Hans Christian Oersted |
| (iii) Suggestion that magnet exerts force on conductor | 3. Michael Faraday |
| (iv) Rule for direction of magnetic field around straight wire | 4. Fleming |
| 5. Maxwell (corkscrew) |
(a) (i)-2, (ii)-4, (iii)-1, (iv)-5
(b) (i)-2, (ii)-1, (iii)-4, (iv)-5
(c) (i)-1, (ii)-4, (iii)-2, (iv)-3
(d) (i)-3, (ii)-5, (iii)-1, (iv)-4
Answer: (a) (i)-2, (ii)-4, (iii)-1, (iv)-5
22. “The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.”
What property of magnetic field lines indicates a uniform magnetic field?
(a) They are circular.
(b) They emerge from the north pole.
(c) They are parallel and equidistant.
(d) They are crowded together.
Answer: (c) They are parallel and equidistant.
23. An electric oven is rated at 2 kW and is operated in a domestic circuit of 220 V. If the circuit has a fuse rated at 5 A, what is likely to happen when the oven is switched on?
(a) The oven will operate normally.
(b) The fuse will melt and break the circuit.
(c) The voltage in the circuit will drop to 100 V.
(d) The oven will consume less than 5 A.
Answer: (b) The fuse will melt and break the circuit.
24. Arrange the following parts of a domestic electrical supply system in the order they are typically encountered by electricity entering a house.
(i) Distribution box with fuses for separate circuits
(ii) Electricity meter
(iii) Main fuse (Electricity Board’s fuse)
(iv) Main switch
(a) (iii) → (ii) → (iv) → (i)
(b) (ii) → (iii) → (iv) → (i)
(c) (iii) → (iv) → (ii) → (i)
(d) (iv) → (ii) → (iii) → (i)
Answer: (a) (iii) → (ii) → (iv) → (i)
25. A student sets up an experiment with a horizontal wire XY, where current flows from X to Y. A compass needle placed directly below the wire deflects with its north pole pointing towards East. If the current direction is reversed (from Y to X), what will be the new direction of deflection of the compass needle’s north pole?
(a) Towards East
(b) Towards West
(c) Towards North
(d) No deflection
Answer: (b) Towards West
26. Assertion (A): The metallic body of an electric appliance like an electric press is connected to the earth wire.
Reason (R): The earth wire provides a high-resistance path for any leakage current, preventing electric shock.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (c) A is true but R is false.
27. Match the device (Column A) with the principle of electromagnetism it primarily utilizes (Column B).
| Column A | Column B |
| (i) Electric Motor | 1. Electromagnetic induction (changing magnetic field induces current) |
| (ii) Electric Generator | 2. Magnetic effect of current (current produces magnetic field) |
| (iii) Electromagnet | 3. Force on a current-carrying conductor in a magnetic field |
| (iv) Loudspeaker | 4. Heating effect of electric current |
(a) (i)-3, (ii)-1, (iii)-2, (iv)-3
(b) (i)-2, (ii)-3, (iii)-1, (iv)-2
(c) (i)-3, (ii)-1, (iii)-4, (iv)-2
(d) (i)-1, (ii)-2, (iii)-3, (iv)-4
Answer: (a) (i)-3, (ii)-1, (iii)-2, (iv)-3
28. “Hans Christian Oersted, in 1820 he accidentally discovered that a compass needle got deflected when an electric current passed through a metallic wire placed nearby.”
What did this accidental discovery primarily demonstrate?
(a) That magnets can produce electric current.
(b) That electricity and magnetism are related phenomena.
(c) The heating effects of electric current.
(d) The chemical effects of electric current.
Answer: (b) That electricity and magnetism are related phenomena.
29. Consider a bar magnet. The magnetic field lines are observed to be most crowded near the poles and less crowded at other locations. What does this observation indicate about the magnetic field strength?
(a) The field is weakest at the poles.
(b) The field is uniform everywhere around the magnet.
(c) The field is strongest at the poles.
(d) The field strength is independent of the crowding of lines.
Answer: (c) The field is strongest at the poles.
30. To demonstrate the force on a current-carrying conductor in a magnetic field, an aluminium rod AB is suspended horizontally. Arrange the following steps to observe the force.
(i) Pass a current through the aluminium rod.
(ii) Place a strong horseshoe magnet such that the rod is between its poles.
(iii) Connect the aluminium rod in series with a battery and a key.
(iv) Observe the displacement of the rod.
(a) (iii) → (ii) → (i) → (iv)
(b) (ii) → (iii) → (i) → (iv)
(c) (iii) → (i) → (ii) → (iv)
(d) (ii) → (i) → (iii) → (iv)
Answer: (b) (ii) → (iii) → (i) → (iv)
Additional Questions and Answers
1. What is a compass needle made of?
Answer: A compass needle is made of a small magnet.
2. What do you call the end of a compass needle that points towards north?
Answer: The end of a compass needle that points towards north is called north seeking or north pole.
3. What do you call the end of a compass needle that points towards south?
Answer: The other end of a compass needle that points towards south is called south seeking or south pole.
4. Define magnetic field.
Answer: The region surrounding a magnet, in which the force of the magnet can be detected, is said to have a magnetic field.
5. What do magnetic field lines represent?
Answer: Field lines are used to represent a magnetic field.
6. Who discovered the magnetic effect of electric current?
Answer: Hans Christian Oersted discovered the magnetic effect of electric current.
7. In which year did Hans Christian Oersted discover the magnetic effect of electric current?
Answer: Hans Christian Oersted discovered the magnetic effect of electric current in 1820.
8. Who proposed that a magnet exerts an equal and opposite force on a current-carrying conductor?
Answer: French scientist Andre Marie Ampere suggested that the magnet must also exert an equal and opposite force on the current-carrying conductor.
9. What is the unit of magnetic field strength named in honour of Hans Christian Oersted?
Answer: The unit of magnetic field strength named in honour of Hans Christian Oersted is the oersted.
10. Which rule describes the direction of the magnetic field around a current-carrying straight conductor?
Answer: The right-hand thumb rule describes the direction of the magnetic field around a current-carrying straight conductor.
11. Which rule is used to determine the direction of force on a current-carrying conductor in a magnetic field?
Answer: Fleming’s left-hand rule is used to determine the direction of force on a current-carrying conductor in a magnetic field.
12. Define solenoid.
Answer: A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called a solenoid.
13. What is an electromagnet?
Answer: An electromagnet consists of a core of soft iron wrapped around with a coil of insulated copper wire.
14. Define short-circuiting.
Answer: When the live wire and the neutral wire come into direct contact, the current in the circuit abruptly increases. This is called short-circuiting.
15. What colour insulation is used for the live wire in domestic circuits?
Answer: Red insulation is used for the live wire in domestic circuits.
16. What colour insulation is used for the neutral wire in domestic circuits?
Answer: Black insulation is used for the neutral wire in domestic circuits.
17. What colour insulation is used for the earth wire in domestic circuits?
Answer: Green insulation is used for the earth wire in domestic circuits.
18. What is the standard potential difference between live and neutral wires in domestic circuits?
Answer: The standard potential difference between live and neutral wires in domestic circuits is 220 V.
19. What is the frequency of the AC power supply in our houses?
Answer: The frequency of the AC power supply in our houses is 50 Hz.
20. What device prevents damage to an electric circuit by melting when the current is too high?
Answer: An electric fuse is the device that prevents damage to an electric circuit by melting when the current is too high.
21. Explain the principle of a fuse and how it protects domestic electric circuits from overloading and short-circuiting.
Answer: An electric fuse is an important component of all domestic circuits. A fuse in a circuit prevents damage to the appliances and the circuit due to overloading. Overloading can occur when the live wire and the neutral wire come into direct contact, which happens when the insulation of wires is damaged or there is a fault in the appliance. In such a situation, the current in the circuit abruptly increases, which is called short-circuiting. The use of an electric fuse prevents the electric circuit and the appliance from possible damage by stopping the flow of unduly high electric current. The Joule heating that takes place in the fuse melts it to break the electric circuit. Overloading can also occur due to an accidental hike in the supply voltage or by connecting too many appliances to a single socket.
22. Describe the safety measures used in domestic wiring and appliances, focusing on the roles of live, neutral and earth wires.
Answer: In our homes, we receive supply of electric power through a main supply. One of the wires in this supply, usually with red insulation cover, is called live wire (or positive). Another wire, with black insulation, is called neutral wire (or negative). The earth wire, which has insulation of green colour, is usually connected to a metal plate deep in the earth near the house. This is used as a safety measure, especially for those appliances that have a metallic body, for example, electric press, toaster, table fan, refrigerator, etc. The metallic body is connected to the earth wire, which provides a low-resistance conducting path for the current. Thus, it ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shock. An electric fuse is an important safety component that prevents damage due to overloading or short-circuiting.
23. How does increasing the number of turns in a circular coil affect the magnetic field produced at its centre?
Answer: If there is a circular coil having n turns, the field produced is n times as large as that produced by a single turn. This is because the current in each circular turn has the same direction, and the field due to each turn then just adds up.
