60+ Questions & Answers - NCERT Based (Class 10)
Structured as Part A (1 mark, short answers), Part B (4 marks, ~6 lines answers), Part C (8 marks, detailed). 20 per part, based on chapter questions/exercises/content.
Part A: 1 Mark Questions (Short Answers)
1. Why does a compass needle get deflected when brought near a bar magnet?
1 Mark Answer: Magnetic field.
2. Draw magnetic field lines around a bar magnet.
1 Mark Answer: Closed curves.
3. List the properties of magnetic field lines.
1 Mark Answer: Closed, no cross.
4. Why don’t two magnetic field lines intersect each other?
1 Mark Answer: Two directions impossible.
5. 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.
1 Mark Answer: Into/out of table.
6. The magnetic field in a given region is uniform. Draw a diagram to represent it.
1 Mark Answer: Parallel lines.
7. Choose the correct option. The magnetic field inside a long straight solenoid-carrying current
1 Mark Answer: Same all points.
8. 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.)
1 Mark Answer: Velocity, momentum.
9. 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?
1 Mark Answer: Increases all.
10. A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
1 Mark Answer: Upward.
11. Name two safety measures commonly used in electric circuits and appliances.
1 Mark Answer: Fuse, earth.
12. 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.
1 Mark Answer: Fuse melts.
13. What precaution should be taken to avoid the overloading of domestic electric circuits?
1 Mark Answer: Proper rating.
14. Which of the following correctly describes the magnetic field near a long straight wire?
1 Mark Answer: Concentric circles.
15. At the time of short circuit, the current in the circuit
1 Mark Answer: Increases heavily.
16. 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. (b) A wire with a green insulation is usually the live wire of an electric supply.
1 Mark Answer: (a) True, (b) False.
17. List two methods of producing magnetic fields.
1 Mark Answer: Current, electromagnet.
18. When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
1 Mark Answer: Perpendicular.
19. 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?
1 Mark Answer: Downward.
20. What is the function of an earth wire? Why is it necessary to earth metallic appliances?
1 Mark Answer: Safety path.
Part B: 4 Marks Questions (Answers in ~6 Lines)
1. Why does a compass needle get deflected when brought near a bar magnet?
4 Marks Answer: Bar magnet produces field. Compass small magnet. Field exerts force. Needle aligns with field. North seeks south. Demonstrates attraction/repulsion.
2. Draw magnetic field lines around a bar magnet.
4 Marks Answer: Lines from north to south outside. Closed curves. Closer near poles stronger. No intersection. Inside south to north. Represent direction, strength.
3. List the properties of magnetic field lines.
4 Marks Answer: Emerge north, merge south. Closed loops. No cross. Closer stronger field. Direction north pole moves. Tangent at point gives direction.
4. Why don’t two magnetic field lines intersect each other?
4 Marks Answer: Intersection means two directions. Compass would point two ways. Impossible. Single direction per point. Ensures unique field vector.
5. 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.
4 Marks Answer: Thumb clockwise, fingers field. Inside into table. Outside out of table. Perpendicular to plane. Stronger at center.
6. The magnetic field in a given region is uniform. Draw a diagram to represent it.
4 Marks Answer: Parallel straight lines. Equal spacing. Arrows same direction. Like inside solenoid. Represents constant strength, direction.
7. Choose the correct option. The magnetic field inside a long straight solenoid-carrying current
4 Marks Answer: (d) Same at all points. Uniform parallel lines. Like bar magnet inside. Ends behave poles. Strength depends current, turns.
8. 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.)
4 Marks Answer: (c) Velocity, (d) momentum. Force perpendicular changes direction. Speed constant. Mass unchanged.
9. 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?
4 Marks Answer: Increases all cases. Force F = I L B sinθ. Higher I, B, L increases F. Displacement proportional.
10. A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
4 Marks Answer: (d) Upward. Fleming’s left-hand: Current west, force north. Field upward.
11. Name two safety measures commonly used in electric circuits and appliances.
4 Marks Answer: Fuse, earth wire. Fuse melts high current. Earth low resistance path. Prevent shocks, damage.
12. 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.
4 Marks Answer: Current 9 A exceeds 5 A. Overload, fuse melts. Circuit breaks. Prevents damage.
13. What precaution should be taken to avoid the overloading of domestic electric circuits?
4 Marks Answer: Proper rating circuits. Avoid many appliances socket. Use fuses. Regular checks.
14. Which of the following correctly describes the magnetic field near a long straight wire?
4 Marks Answer: (d) Concentric circles. Perpendicular plane. Direction right-hand rule. Strength decreases distance.
15. At the time of short circuit, the current in the circuit
4 Marks Answer: (c) Increases heavily. Low resistance path. Sudden surge. Fuse melts.
16. 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. (b) A wire with a green insulation is usually the live wire of an electric supply.
4 Marks Answer: (a) True, straight at center. (b) False, green earth. Red live.
17. List two methods of producing magnetic fields.
4 Marks Answer: Current wire. Electromagnet coil. Bar magnet natural. Solenoid.
18. When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
4 Marks Answer: Perpendicular current field. Sinθ =1. Maximum F. Right angles.
19. 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?
4 Marks Answer: Downward. Electron opposite current. Force right, field down.
20. What is the function of an earth wire? Why is it necessary to earth metallic appliances?
4 Marks Answer: Low resistance path leakage. Prevents shock. Earths body potential. Safety metallic.
Part C: 8 Marks Questions (Detailed Answers)
1. Why does a compass needle get deflected when brought near a bar magnet?
8 Marks Answer: A bar magnet produces a magnetic field in the surrounding region, exerting a force on other magnetic materials. The compass needle is itself a small bar magnet with north and south poles. When brought near the bar magnet, the needle aligns with the field lines due to torque from attraction and repulsion. The north pole of the compass is attracted to the south pole of the bar magnet and repelled by the north pole, causing deflection. This demonstrates that magnetic fields interact, and the direction is such that the needle points along the field lines. In experiments, this deflection is used to map field patterns, showing fields are vector quantities with direction from north to south outside the magnet.
2. Draw magnetic field lines around a bar magnet.
8 Marks Answer: Magnetic field lines around a bar magnet are closed curves emerging from the north pole and merging at the south pole outside the magnet. Inside, they run from south to north, forming continuous loops. The lines are denser near the poles, indicating stronger field strength there. No two lines intersect, as that would imply two directions at one point, which is impossible. To draw, start from the north pole, curve towards the south, and ensure even spacing away from poles where the field weakens. This pattern can be visualized using iron filings or a compass, where the needle aligns tangent to the lines. The diagram represents the direction a free north pole would move.
3. List the properties of magnetic field lines.
8 Marks Answer: Magnetic field lines are imaginary closed curves representing the field direction and strength. They emerge from the north pole and merge at the south pole outside a magnet, while inside they go from south to north. The lines never intersect, ensuring a unique direction at each point. Closer lines indicate stronger fields, as seen near poles. The tangent at any point gives the field direction, which is the path a hypothetical north pole would follow. In uniform fields, lines are parallel and equidistant. These properties help visualize fields produced by currents or magnets, and are used in rules like right-hand thumb for current-carrying wires.
4. Why don’t two magnetic field lines intersect each other?
8 Marks Answer: If two magnetic field lines intersected, it would mean that at the intersection point, the magnetic field has two different directions simultaneously. A compass needle placed there would point in two directions at once, which is physically impossible. Magnetic fields are vector quantities with a single magnitude and direction at each point in space. Non-intersection ensures consistency in field representation. This property holds for all fields, whether from bar magnets, current wires, or solenoids. In diagrams, lines are drawn to avoid crossing, reflecting real behavior observed in experiments with iron filings or compasses.
5. 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.
8 Marks Answer: For a circular loop with clockwise current (viewed from above), apply the right-hand thumb rule: Curl fingers clockwise, thumb points into the table for inside field. Outside, field is out of the table. The field is perpendicular to the loop plane, stronger at the center where lines are straight. Away, lines become larger arcs. This is because each wire segment contributes to the field in the same direction inside. The pattern resembles a bar magnet, with one face north and the other south. Experiments with iron filings show concentric circles becoming straight at center.
6. The magnetic field in a given region is uniform. Draw a diagram to represent it.
8 Marks Answer: A uniform magnetic field is represented by parallel straight lines with equal spacing, all pointing in the same direction, indicated by arrows. For example, inside a long solenoid, the lines are parallel from one end to the other, showing constant strength and direction. No crowding or spreading, unlike near bar magnet poles. The diagram would show lines from left to right or north to south, with arrows. This uniformity means the force on a pole is the same everywhere. Observed in solenoids or between flat magnet poles, useful in devices like motors for consistent force.
7. Choose the correct option. The magnetic field inside a long straight solenoid-carrying current
8 Marks Answer: (d) is the same at all points. The field inside a solenoid is uniform, consisting of parallel straight lines along the axis, independent of position inside. This is because the coil turns produce additive fields, creating a strong, consistent field like a bar magnet. Near the ends, it weakens slightly, but ideally uniform. The strength depends on current, turns per length, but not location inside. This property makes solenoids useful for electromagnets needing constant fields.
8. 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.)
8 Marks Answer: (c) velocity (d) momentum. A magnetic field exerts force perpendicular to velocity, changing direction but not speed. Thus, velocity vector changes (direction), and momentum (mass times velocity) also changes direction. Mass and speed remain constant. For charged particles like protons, path is circular or helical. This is basis for cyclotrons. No work done, kinetic energy unchanged.
9. 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?
8 Marks Answer: Displacement increases in all cases. The force F = B I L sinθ, where B is field, I current, L length, θ=90° sinθ=1. (i) Higher I increases F directly. (ii) Stronger magnet increases B, thus F. (iii) Longer rod increases L, thus F. Larger force causes greater displacement. Activity shows force perpendicular to field and current. Reverse current or field reverses direction. Basis for motor working.
10. A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
8 Marks Answer: (d) upward. Using Fleming’s left-hand rule for positive charge: Middle finger west (velocity as current), thumb north (force). Forefinger points upward for field. Alpha particle positive, so current direction same as velocity. Field perpendicular to both. Recall rule: Force, field, current mutually perpendicular. This determines field direction in experiments.
11. Name two safety measures commonly used in electric circuits and appliances.
8 Marks Answer: Fuse and earth wire. Fuse is a thin wire melting at high current, breaking circuit to prevent overload or short-circuit damage. Placed in live wire. Earth wire connects metallic body to earth, providing low-resistance path for leakage current, keeping body at earth potential to avoid shocks. Green insulation. Used in appliances like irons. Ensures user safety by earthing faults. Both prevent fires, shocks in domestic circuits.
12. 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.
8 Marks Answer: Current drawn I = P/V = 2000/220 ≈ 9 A, exceeding 5 A rating. Circuit overloads, fuse melts to break circuit. Prevents heating, fire. Explanation: Power rating indicates maximum safe current; exceeding causes resistance heating. Fuse designed to melt at rating, protecting wiring. Always match appliance power to circuit capacity.
13. What precaution should be taken to avoid the overloading of domestic electric circuits?
8 Marks Answer: Use circuits with proper current ratings like 5 A for low power, 15 A for high. Avoid connecting too many appliances to one socket. Install fuses or circuit breakers. Regular insulation checks prevent short-circuits. Distribute load across circuits. Earth metallic appliances. This prevents excessive current, heating, fires. Overloading from accidental hikes or faults; precautions ensure safety.
14. Which of the following correctly describes the magnetic field near a long straight wire?
8 Marks Answer: (d) The field consists of concentric circles centred on the wire. Field perpendicular to wire, direction by right-hand thumb rule. Circles larger away, weaker field. No radial or straight lines. Observed with iron filings or compass. Strength inversely proportional to distance. Basis for Oersted discovery.
15. At the time of short circuit, the current in the circuit
8 Marks Answer: (c) increases heavily. Short-circuit creates low-resistance path between live and neutral, bypassing load. Current surges abruptly due to minimal resistance. Can cause sparking, fire. Fuse melts to stop flow. Occurs from damaged insulation or faults. Prevents by proper wiring, insulation.
16. 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. (b) A wire with a green insulation is usually the live wire of an electric supply.
8 Marks Answer: (a) True: At center, arcs appear straight, parallel. (b) False: Green is earth wire; live is red. Statement (a) from loop field becoming straight at center due to additive contributions. (b) Color coding: Red live, black neutral, green earth for safety identification.
17. List two methods of producing magnetic fields.
8 Marks Answer: Passing current through conductor like straight wire or coil produces field. Using permanent bar magnets. Current method: Oersted, field concentric or uniform in solenoid. Permanent: Natural, field lines closed. Electromagnets combine, iron core enhances. Applications: Motors from current fields, compasses from permanent.
18. When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
8 Marks Answer: When current perpendicular to field, θ=90°, sinθ=1, F maximum. F = B I L sinθ. At other angles, less. Observed in activity with rod; maximum displacement at right angles. Basis for Fleming’s rule. Used in motors for maximum torque.
19. 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?
8 Marks Answer: Downward. Electron beam current opposite velocity (front to back). Force right. By Fleming’s left-hand: Middle back to front (opposite electron), thumb right, forefinger down for field. Rule for positive; reverse for negative charge. Determines field in particle deflection experiments.
20. What is the function of an earth wire? Why is it necessary to earth metallic appliances?
8 Marks Answer: Earth wire provides low-resistance path to ground for fault current, preventing shock. Connected to metallic body and earth plate. Leakage current flows to earth, not user. Necessary for appliances like irons, fridges with metal casings prone to faults. Keeps body at earth potential. Green insulation. Safety measure in domestic circuits.
Practice Tip: Time yourself; use diagrams for long Q.
