Magnetic Effects of Electric Current · Class 10 Science: 80 flashcards
All 80 flashcards from this kit, free and with no sign-up.
1. What is a magnetic field?
Show the answer
The space surrounding a magnet throughout which its pull can still be picked up; it has both magnitude and direction.
2. How is the direction of a magnetic field at a point defined?
Show the answer
It is the direction in which the north pole of a small compass needle points when placed at that point.
3. In which direction do field lines run OUTSIDE a bar magnet?
Show the answer
From the north pole to the south pole.
4. In which direction do field lines run INSIDE the magnet?
Show the answer
From the south pole to the north pole — making each field line a closed curve.
5. What does crowding of field lines indicate?
Show the answer
A stronger magnetic field — the field is strongest near the poles where the lines converge.
6. Why can two magnetic field lines never intersect?
Show the answer
At the point of intersection the field would have two directions simultaneously, which is impossible — a compass there can point only one way.
7. What is the surest test that an object is a magnet?
Show the answer
Repulsion — only a magnet can repel another magnet. (Attraction also occurs with ordinary iron.)
8. What happens when you cut a bar magnet in half?
Show the answer
You get two complete magnets, each with its own north and south pole. Isolated poles do not exist.
9. Describe Oersted's observation.
Show the answer
A compass needle placed near a current-carrying wire deflects when current flows, and deflects the opposite way when the current reverses.
10. What conclusion follows from Oersted's experiment?
Show the answer
An electric current produces a magnetic field around the conductor — electricity and magnetism are linked phenomena.
11. Why does a freely suspended bar magnet rest along north-south?
Show the answer
Earth has its own magnetic field; the magnet aligns with Earth's field lines like a huge compass needle.
12. What is the tangent to a field line at a point equal to?
Show the answer
The direction of the magnetic field at that point.
13. Where is a bar magnet's field the weakest in a typical diagram?
Show the answer
Far from the magnet and near the middle region between the poles, where the lines are most spread out.
14. How do iron filings reveal field lines?
Show the answer
Each filing becomes a small induced magnet and aligns with the local field; together they form chains along the field lines.
15. Are magnetic field lines real objects?
Show the answer
No — they are a mapping tool. The field is real; the lines visualise its direction (tangent) and strength (density).
16. What are the two ends of a magnet called and how do they interact?
Show the answer
North and south poles; like poles repel and unlike poles attract.
17. What happens to a compass needle at the exact centre between two identical opposite poles facing each other?
Show the answer
It aligns along the straight, uniform field between the poles (N to S of the gap).
18. Name the scientist whose experiment linked current and magnetism, and the year.
Show the answer
Hans Christian Oersted, in 1820.
19. Draw-rule: how should field lines be spaced in a diagram near vs far from the magnet?
Show the answer
Closer together near the poles (strong field) and progressively farther apart away from the magnet (weakening field).
20. What does a stronger deflection of a compass needle near a wire indicate?
Show the answer
A stronger magnetic field at that spot — either a larger current or a smaller distance from the wire.
21. Describe the magnetic field pattern around a straight current-carrying conductor.
Show the answer
Concentric circles centred on the wire, lying in planes perpendicular to it; the circles spread farther apart with distance as the field weakens.
22. State the right-hand thumb rule.
Show the answer
Grip the wire with the right hand with the thumb pointing along the current; the curled fingers then point in the direction of the magnetic field circles around it.
23. How does the field of a straight wire change with (a) current, (b) distance?
Show the answer
(a) It increases as the current increases. (b) It decreases as the distance from the wire increases.
24. What happens to the field pattern when the current in a wire is reversed?
Show the answer
The field keeps the same circular shape and strength but reverses direction — every circle now runs the other way.
25. Why are the field lines nearly straight at the centre of a current loop?
Show the answer
Every segment of the loop produces circular field arcs; at the centre these arcs all point the same way (perpendicular to the loop's plane) and combine into an almost straight line.
26. How does the field at the centre of a coil depend on the number of turns?
Show the answer
It is directly proportional — a coil of n turns produces n times the field of a single turn, since each turn's field adds in the same direction.
27. State the clock rule for the polarity of a coil's face.
Show the answer
Looking at the face: if the current flows anticlockwise, that face is a north pole; if clockwise, it is a south pole.
28. What is a solenoid?
Show the answer
A coil of many circular turns of insulated copper wire wound closely in the shape of a cylinder.
29. Compare the field of a solenoid with that of a bar magnet.
Show the answer
They are identical in pattern — closed loops emerging from one end (which behaves as N) and entering the other (S); one end of the solenoid acts as a north pole and the other as a south pole.
30. Describe the field INSIDE a solenoid.
Show the answer
Uniform — the field lines are straight, parallel and equally spaced, meaning the field has the same magnitude and direction at every point inside.
31. What is an electromagnet?
Show the answer
A temporary strong magnet made by placing a soft iron core inside a current-carrying solenoid; it is magnetic only while the current flows.
32. Why is soft iron used as the electromagnet's core instead of steel?
Show the answer
Soft iron magnetises very strongly and loses its magnetism as soon as the current stops — ideal for a temporary magnet. Steel would retain magnetism after switch-off.
33. List three ways to increase the strength of an electromagnet.
Show the answer
(1) Increase the number of turns in the coil, (2) increase the current, (3) use a soft iron core (or a thicker one).
34. What kind of magnet is made using a STEEL core in a solenoid?
Show the answer
A permanent magnet — steel retains the magnetism acquired even after the current stops.
35. Give three uses of electromagnets.
Show the answer
Electric bells, scrapyard cranes for lifting heavy iron, relays and magnetic locks (also loudspeakers, maglev trains, MRI machines).
36. Why must the solenoid's wire be insulated?
Show the answer
Without insulation, adjacent turns would short-circuit through each other and current would not travel around the loops — no proper field would form.
37. How can you find which end of a current-carrying solenoid is the north pole?
Show the answer
Look at an end face and apply the clock rule (anticlockwise = N), or grip the solenoid with the right hand, fingers curling along the current in the turns — the thumb points toward the north end.
38. An electric bell rings continuously while the switch is pressed. What makes the hammer vibrate?
Show the answer
The electromagnet pulls the hammer, which breaks the circuit contact, killing the magnetism; a spring pulls the hammer back, remaking the contact — the cycle repeats rapidly.
39. In the iron-filing demonstration of a straight wire's field, why do the circles fade with distance?
Show the answer
The field weakens inversely with distance from the wire, so farther filings feel too weak a field to align into visible rings.
40. Does a current-carrying straight wire have magnetic poles?
Show the answer
No — its field forms closed circles around it with no N or S; poles appear only for loops, coils and solenoids where the field enters/leaves the faces.
41. What happens when a current-carrying conductor is placed in a magnetic field?
Show the answer
It experiences a mechanical force, produced by the interaction between its own magnetic field and the external field.
42. State Fleming's left-hand rule.
Show the answer
Stretch the thumb, forefinger and second finger of the LEFT hand mutually perpendicular. If the forefinger points along the field (N to S) and the second finger along the current, the thumb gives the direction of the force (motion) on the conductor.
43. In Fleming's rule, what does each finger represent?
Show the answer
Forefinger — magnetic Field; second (middle) finger — Current; thumb — Motion (force).
44. When is the force on a current-carrying conductor maximum?
Show the answer
When the direction of the current is perpendicular (at 90°) to the direction of the magnetic field.
45. When is the force zero?
Show the answer
When the current is parallel (or antiparallel) to the magnetic field — no perpendicular component, no force.
46. What happens to the force if the current is reversed?
Show the answer
The force reverses its direction.
47. What happens if BOTH the current and the field are reversed?
Show the answer
The force direction remains unchanged — the two reversals cancel.
48. Name three factors that increase the force on the conductor.
Show the answer
A larger current, a stronger magnetic field, and a greater length of the conductor lying inside the field.
49. Which hand is used for the force rule and which for the field-around-a-wire rule?
Show the answer
LEFT hand for Fleming's force rule; RIGHT hand for the thumb-grip rule giving the field circles around a current.
50. Describe the aluminium-rod demonstration in one line.
Show the answer
A rod hanging between the poles of a horseshoe magnet jerks sideways when current flows, reversing its jerk when the current or the field is reversed.
51. Field into the page, current to the right — which way is the force?
Show the answer
Upward (up the page), by Fleming's left-hand rule — forefinger into the page, second finger to the right, thumb up.
52. Field from left to right (in the page), current out of the page — force direction?
Show the answer
Upward (up the page). Forefinger to the right, second finger out of the page toward you — the thumb points up.
53. How does an electric motor use this force?
Show the answer
The two side arms of its coil carry current in opposite directions within the same field, so they feel opposite forces — a turning pair that rotates the coil about its axle.
54. How does a loudspeaker use this force?
Show the answer
The varying audio current in a coil (attached to the cone, sitting in a magnet's field) produces a varying force that vibrates the cone, generating sound waves.
55. What does a galvanometer measure and how?
Show the answer
It detects/measures small currents: the current-carrying coil in a magnetic field twists against a spring, and the deflection of its pointer is proportional to the current.
56. Does a wire with NO current experience this magnetic force?
Show the answer
No — the force requires a current. (A steady magnetic field exerts no net force on a stationary, current-free wire.)
57. Does the force act on free moving charges like an electron beam?
Show the answer
Yes — a moving charge is a current. For electrons, apply Fleming's rule with the current direction OPPOSITE to the electron velocity.
58. A vertical wire in a horizontal field pointing north carries current upward. Find the force direction.
Show the answer
Toward the west. (Forefinger north, second finger up — thumb points west.)
59. Why does the rod in the demonstration move at all — where does the push physically come from?
Show the answer
The rod's own circular field adds to the external field on one side of the rod and opposes it on the other; the rod is pushed from the stronger-field side toward the weaker-field side.
60. Name four everyday devices built on the force on a current in a field.
Show the answer
Electric motors (fans, mixers, EVs), loudspeakers, galvanometers/ammeters/voltmeters, and microphone-style actuators (also maglev propulsion).
61. Name the three wires in a domestic supply with their insulation colours.
Show the answer
Live wire — red; neutral wire — black; earth wire — green.
62. What is the potential difference between the live and neutral wires in India?
Show the answer
220 V.
63. What is the potential of the neutral wire?
Show the answer
Approximately zero — it is the return path that completes the circuit.
64. What is the earth wire connected to?
Show the answer
A metal plate buried deep in the earth (moist soil) near the house — giving fault currents a low-resistance path into the ground.
65. In which wire are the fuse and all switches connected, and why?
Show the answer
In the LIVE wire — so that switching off (or a blown fuse) disconnects the appliance from the high 220 V potential, making it safe to touch.
66. What are the two separate circuits commonly used in homes?
Show the answer
A 5 A circuit for low-power devices (bulbs, fans) and a 15 A circuit for high-power appliances (geysers, ACs, irons) — each with its own fuse.
67. How are all domestic appliances connected — series or parallel? Give two reasons.
Show the answer
In parallel: each gets the full 220 V it is designed for, and each can be switched independently (a fault in one doesn't stop the rest).
68. What is earthing of an appliance?
Show the answer
Connecting its metal body to the earth wire (through the 3-pin plug's top pin), so any leaking current flows into the ground instead of through a person.
69. Which appliances must compulsorily be earthed?
Show the answer
Appliances with metal bodies — electric iron, geyser, refrigerator, mixer, toaster, washing machine.
70. What happens when the live wire accidentally touches an earthed metal body?
Show the answer
A large current flows through the earth wire to the ground; this fault current blows the fuse, disconnecting the supply — the user is protected.
71. Define a short circuit.
Show the answer
The direct touching of the live and neutral wires (usually through damaged insulation), reducing the resistance almost to zero so that a very large current flows.
72. Define overloading.
Show the answer
The drawing of more current through a circuit than its rated safe limit — usually by connecting too many high-power appliances to it at once, or by a voltage surge.
73. State two causes of overloading.
Show the answer
(1) Connecting too many appliances to a single socket/circuit. (2) An accidental sudden rise in the supply voltage. (Also: using an appliance beyond the circuit's rating.)
74. How does the fuse protect against both short circuits and overloading?
Show the answer
Both faults push the current above the fuse's rating; the excess current's I²R heat melts the fuse wire immediately, breaking the circuit before the house wiring overheats.
75. Why is the earth pin of a 3-pin plug longer and thicker?
Show the answer
Longer — so the earth connects first (and disconnects last) for safety; thicker — so it cannot be inserted into the live or neutral holes by mistake.
76. What does an MCB do?
Show the answer
A Miniature Circuit Breaker trips (switches off) automatically when the current exceeds its rating — a resettable, reusable replacement for the fuse.
77. What is the sequence of components from the supply pole into the house?
Show the answer
Supply → main fuse (in the live wire) → electricity meter → main switch → distribution to the parallel household circuits.
78. Why shouldn't many heavy appliances be run from one socket via a multi-plug?
Show the answer
Their combined current can exceed the circuit's rated limit — overloading — overheating the wiring and risking fire before the fuse blows.
79. Why is it dangerous to touch electrical appliances with wet hands?
Show the answer
Water sharply lowers the skin's resistance, so even a small leaking voltage can drive a dangerously large current through the body.
80. What is the function of the electricity meter?
Show the answer
It records the electrical energy consumed by the household in kilowatt-hours (units), for billing.
Your notes can be a kit like these
Every kit here was made from real study material. Point Veda at a chapter, a PDF, a photo or a link and get notes, flashcards, practice MCQs, games and a scored test — free, in 42 languages.
- Chapter notes
- Flashcards
- Practice MCQs
- Scored tests
- Exam prep
Get Veda free See what students get
Free to start · No ads · Works in 42 languages