1. What is a magnet?
A material that attracts iron and produces a magnetic field.
2. What is a magnetic field?
The region around a magnet where magnetic forces act.
3. What are magnetic poles?
The ends of a magnet, north and south, where force is strongest.
4. What happens when like poles are brought together?
Like poles (N-N or S-S) repel each other.
5. What happens when unlike poles are brought together?
Unlike poles (N-S) attract each other.
6. What is a magnetic field line?
An imaginary line showing the direction of magnetic force.
7. What is the direction of magnetic field lines?
They emerge from the north pole and enter the south pole.
8. What is a permanent magnet?
A magnet retaining its magnetism without external influence.
9. What is a temporary magnet?
A magnet that loses magnetism when the cause is removed.
10. What materials are attracted by magnets?
Iron, nickel, and cobalt are attracted by magnets.
11. What is the Earthâs magnetic field?
A natural field behaving like a bar magnet inside Earth.
12. Where is the Earthâs magnetic north pole?
It is near the geographic south pole.
13. What is a compass?
A device with a magnetic needle showing direction.
14. How does a compass work?
Its needle aligns with Earthâs magnetic field, pointing north.
15. What is the shape of a magnetic field around a bar magnet?
It forms closed loops from north to south outside the magnet.
16. What is a uniform magnetic field?
A field with constant strength and direction.
17. What is a non-uniform magnetic field?
A field with varying strength or direction.
18. How can magnetic field lines be visualized?
Using iron filings or a compass to trace the pattern.
19. What happens if a magnet is broken?
Each piece becomes a magnet with north and south poles.
20. What is magnetic force?
The force exerted by a magnet on magnetic materials.
21. What is the magnetic effect of electric current?
A current-carrying conductor produces a magnetic field.
22. Who discovered the magnetic effect of current?
Hans Christian Oersted discovered it in 1820.
23. What happens when current flows through a wire?
A magnetic field forms around the wire.
24. What is the shape of the magnetic field around a straight wire?
It forms concentric circles around the wire.
25. What determines the strength of the magnetic field around a wire?
The current strength and distance from the wire.
26. What is the right-hand grip rule for a straight conductor?
Fingers curl in the field direction when thumb points to current.
27. What happens if current direction reverses in a wire?
The magnetic field direction reverses too.
28. What is a solenoid?
A coil of wire producing a magnetic field when current flows.
29. What is the magnetic field inside a solenoid?
It is uniform and parallel to the solenoidâs axis.
30. What is the magnetic field outside a solenoid?
It is weak and resembles a bar magnetâs field.
31. What is the right-hand rule for a solenoid?
Fingers curl with current, thumb points to the north pole.
32. What factors increase a solenoidâs magnetic field?
More turns, higher current, and an iron core increase it.
33. What is an electromagnet?
A temporary magnet made by current in a solenoid with a core.
34. What is the core material in an electromagnet?
Soft iron is commonly used for its magnetic properties.
35. What happens when current stops in an electromagnet?
It loses its magnetism without current.
36. What is the use of an electromagnet?
Itâs used in cranes, bells, and electric motors.
37. What is the magnetic field pattern of a circular loop?
It forms circular loops, strongest at the center.
38. What happens to the field if current in a loop increases?
The magnetic field strength increases proportionally.
39. What is the direction of the field at the center of a loop?
Itâs perpendicular to the loopâs plane (right-hand rule).
40. What is the magnetic fieldâs strength proportional to?
Itâs proportional to current and inversely to distance.
41. What is the motor effect?
A force acts on a current-carrying conductor in a magnetic field.
42. What causes the force on a conductor?
Interaction between the conductorâs field and external field.
43. What is Flemingâs Left-Hand Rule?
Fingers show force when current and field directions align.
44. How is Flemingâs Left-Hand Rule applied?
Index finger (current), middle (field), thumb (force).
45. What is the direction of force if current and field are parallel?
No force acts; they must be perpendicular.
46. What factors affect the force on a conductor?
Current, field strength, and conductor length affect it.
47. What is the formula for force on a conductor?
F
48. What is the force if B
49. What is the unit of magnetic field strength?
It is tesla (T) in the SI system.
50. What is 1 tesla?
1 T is 1 newton per ampere-meter of force.
51. What is an electric motor?
A device converting electrical energy to mechanical energy.
52. What is the principle of an electric motor?
It uses the force on a current-carrying conductor in a field.
53. What are the main parts of an electric motor?
Armature, magnets, commutator, and brushes.
54. What is the armature in a motor?
A coil of wire that rotates in the magnetic field.
55. What is the role of the commutator?
It reverses current direction to keep the motor rotating.
56. What are brushes in a motor?
Carbon contacts supplying current to the commutator.
57. What provides the magnetic field in a motor?
Permanent magnets or electromagnets create the field.
58. How does a motor rotate continuously?
The commutator reverses current every half-turn.
59. What is the direction of rotation in a motor?
Determined by Flemingâs Left-Hand Rule.
60. What happens if current increases in a motor?
The force and rotation speed increase.
61. What is the use of an electric motor?
It powers fans, pumps, and machines.
62. What is a DC motor?
A motor running on direct current with a commutator.
63. What happens if the magnetic field weakens?
The motorâs force and speed decrease.
64. What is the split ring in a motor?
Another name for the commutator reversing current.
65. What is the torque in a motor?
The rotational force causing the armature to turn.
66. What is the role of the axle in a motor?
It supports the armature and transfers rotation.
67. What happens if brushes wear out?
Current supply stops, halting the motor.
68. What is the efficiency of a motor?
The ratio of mechanical output to electrical input.
69. What powers a simple DC motor?
A battery supplies direct current to the motor.
70. What is the effect of more coil turns in a motor?
It increases the force and torque.
71. What is electromagnetic induction?
Generating current by changing a magnetic field.
72. Who discovered electromagnetic induction?
Michael Faraday discovered it in 1831.
73. What induces an electric current?
Relative motion between a conductor and magnetic field.
74. What is Faradayâs Law of induction?
Induced EMF is proportional to the rate of field change.
75. What is the formula for induced EMF?
EMF
76. What is magnetic flux?
The amount of magnetic field passing through an area.
77. What is the unit of magnetic flux?
It is weber (Wb) in the SI system.
78. What is 1 weber?
1 Wb is 1 tesla-meter² of magnetic flux.
79. What is Lenzâs Law?
Induced current opposes the change causing it.
80. What is Flemingâs Right-Hand Rule?
It determines the direction of induced current.
81. How is Flemingâs Right-Hand Rule applied?
Index (field), middle (motion), thumb (current).
82. What increases induced EMF?
More turns, stronger field, or faster motion increase it.
83. What is the direction of induced current in a coil?
It follows Lenzâs Law to oppose field change.
84. What is an induced current?
Current produced by changing magnetic flux.
85. What is the role of a magnet in induction?
It provides the changing field to induce current.
86. What happens if a coil moves in a uniform field?
No current is induced without flux change.
87. What is the use of electromagnetic induction?
It generates electricity in dynamos and transformers.
88. What is mutual induction?
Current in one coil induces current in another nearby coil.
89. What is self-induction?
Current change in a coil induces EMF in itself.
90. What is the unit of induced EMF?
It is volt (V), same as potential difference.
91. What is an electric generator?
A device converting mechanical energy to electrical energy.
92. What is the principle of a generator?
It uses electromagnetic induction to produce current.
93. What are the main parts of a generator?
Armature, magnets, slip rings, and brushes.
94. What is the armature in a generator?
A coil rotating in a magnetic field to induce current.
95. What is the role of slip rings?
They maintain continuous contact for AC output.
96. What are brushes in a generator?
Carbon contacts transferring current from slip rings.
97. What is an AC generator?
A generator producing alternating current with slip rings.
98. What is a DC generator?
A generator producing direct current with a commutator.
99. What provides the magnetic field in a generator?
100. How does an AC generator work?
Rotating coil induces alternating EMF with slip rings.
101. How does a DC generator work?
Rotating coil with a commutator gives unidirectional current.
102. What is the direction of current in an AC generator?
It reverses every half rotation of the coil.
103. What is the direction of current in a DC generator?
It remains constant due to the commutator.
104. What increases the output of a generator?
More turns, stronger field, or faster rotation increase it.
105. What is the use of a generator?
It produces electricity in power plants and homes.
106. What is the frequency of AC in India?
It is 50 Hz, reversing 50 times per second.
107. What is the role of the axle in a generator?
It rotates the armature to induce current.
108. What happens if the field strength increases?
The induced EMF and current increase.
109. What is the difference between motor and generator?
Motor converts electricity to motion; generator does the reverse.
110. What is the efficiency of a generator?
The ratio of electrical output to mechanical input.
111. What is a domestic electric circuit?
A wiring system distributing electricity in homes.
112. What is the standard voltage in India?
It is 220-240 V at 50 Hz AC.
113. What is a live wire?
A wire carrying current at high voltage.
114. What is a neutral wire?
A wire completing the circuit at zero voltage.
115. What is an earth wire?
A safety wire grounding excess current.
116. What is the color of a live wire in India?
It is red or brown.
117. What is the color of a neutral wire in India?
It is black or blue.
118. What is the color of an earth wire in India?
It is green or yellow-green.
119. What is earthing?
Connecting appliances to ground to prevent shocks.
120. What is a fuse?
A safety device melting at high current to break the circuit.
121. What is the material of a fuse wire?
A low-melting-point alloy like tin-lead is used.
122. What is the purpose of a fuse?
It protects circuits from overloading or short circuits.
123. What is an MCB?
Miniature Circuit Breaker trips during overloads.
124. What is the advantage of an MCB over a fuse?
It can be reset, unlike a fuse that melts.
125. What is overloading?
Excessive current drawn beyond circuit capacity.
126. What causes a short circuit?
Direct contact between live and neutral wires.
127. What is a switch in a circuit?
A device to control the flow of current.
128. What is the role of a main switch?
It controls power supply to the entire house.
129. What is a circuit breaker?
A device cutting off current during faults.
130. What is the power rating of appliances?
It shows voltage and power usage, e.g., 220 V, 1000 W.
131. What is the magnetic field strength if F
B
132. What is the force if B
133. What is the magnetic field of a solenoid with n turns?
134. What is Îźâ in the magnetic field formula?
Permeability of free space, 4Ď Ă 10âťâˇ T¡m/A.
135. What is the field if Îźâ
136. What is the induced EMF if N
137. What is the flux if B
ÎŚ
138. What is the force direction if current is upward and field is right?
Force is out of the plane (Flemingâs Left-Hand Rule).
139. What is the current if EMF
I
140. What is the power of a motor with V
P
141. What is the magnetic effect of a 5 A current in a wire?
It produces a stronger field than a lower current.
142. What is the field direction if current flows north?
Circular field is clockwise viewed from the south end.
143. What is the torque on a coil in a motor?
Torque
144. What is the use of a galvanometer in circuits?
It detects small currents or magnetic effects.
145. What is the deflection in a galvanometer?
It shows the presence and direction of current.
146. What is a transformer?
A device changing AC voltage using mutual induction.
147. What is a step-up transformer?
It increases voltage and decreases current.
148. What is a step-down transformer?
It decreases voltage and increases current.
149. What is the principle of a transformer?
It works on mutual induction between coils.
150. What is the turns ratio in a transformer?
Vâ/Vâ
151. What is the voltage if Nâ/Nâ
Vâ
152. What is the voltage if Nâ/Nâ
153. What is the power in a transformer?
Input power (VâIâ) equals output power (VâIâ), ideally.
154. What is the current if P
155. What is the role of a soft iron core in a transformer?
It enhances magnetic flux between coils.
156. What is eddy current?
Induced currents in a core causing energy loss.
157. How are eddy currents reduced?
Using laminated cores minimizes eddy currents.
158. What is the efficiency of a transformer?
The ratio of output power to input power.
159. What is the use of a transformer in power supply?
It adjusts voltage for transmission and use.
160. What is the magnetic field inside a current loop?
Itâs strongest and uniform at the center.
161. What is an electric bell?
A device using an electromagnet to ring a bell.
162. How does an electric bell work?
Current in an electromagnet pulls an armature to strike a gong.
163. What is the role of the interrupter in a bell?
It breaks the circuit to repeat the ringing cycle.
164. What is an electric crane?
A device using electromagnets to lift magnetic materials.
165. What is the advantage of an electromagnet in cranes?
It can release loads by switching off current.
166. What is a relay?
An electromagnetic switch controlling high-power devices.
167. What is the use of a relay?
It safely controls large currents with a small signal.
168. What is the danger of magnetic fields near appliances?
They can interfere with electronic devices.
169. What is the safety feature in domestic circuits?
Earthing and fuses protect against faults.
170. What is the current in a 220 V, 1100 W appliance?
171. What is the magnetic effect in a short circuit?
High current creates a strong magnetic field.
172. What is the role of a fuse in magnetic circuits?
It prevents damage from excessive current flow.
173. What is the magnetic field near a power line?
It forms circular patterns around the wire.
174. What is the use of a motor in a fan?
It rotates blades to circulate air.
175. What is the use of a generator in emergencies?
It provides power during outages using fuel.
176. What is the magnetic field due to Earth?
Itâs about 25-65 ÎźT, varying by location.
177. What is a magnetic dipole?
A magnet with distinct north and south poles.
178. What is the magnetic moment?
A measure of a magnetâs strength and orientation.
179. What is the unit of magnetic moment?
It is ampere-meter² (A¡m²).
180. What is the magnetic field at the poles of a solenoid?
Itâs half the strength of the field inside.
181. What is the effect of doubling current in a solenoid?
The magnetic field strength doubles.
182. What is the field if a solenoid has 500 turns/m and I
183. What is the induced EMF if flux changes from 0.2 Wb to 0.1 Wb in 0.1 s?
184. What is the torque if N
185. What is the use of magnetic shielding?
It protects devices from external magnetic fields.
186. What is the magnetic field near a transformer?
Itâs strong due to alternating current in coils.
187. What is the effect of a stronger magnet in a motor?
It increases torque and rotation speed.
188. What is the frequency of AC in a generator?
It depends on rotation speed and pole pairs.
189. What is the effect of increasing coil area in a generator?
It increases the magnetic flux and induced EMF.
190. What is the magnetic field strength at the center of a circular loop?
191. What is the field if I
192. What is the purpose of laminating the core in a transformer?
It reduces eddy current losses by breaking current paths.
193. What is the magnetic field direction inside a current-carrying loop?
It points perpendicularly through the loopâs plane.
194. What happens if a conductor moves parallel to a magnetic field?
No EMF is induced as thereâs no flux change.
195. What is the role of a dynamo?
It generates electricity using mechanical rotation.
196. What is the difference between AC and DC generators?
AC uses slip rings; DC uses a commutator.
197. What is the effect of reversing the magnetâs poles in a motor?
The direction of rotation reverses.
198. What is the magnetic field pattern of two parallel wires with current?
Fields combine or cancel based on current directions.
199. What happens if currents in parallel wires flow in the same direction?
The wires attract due to aligned magnetic fields.
200. What happens if currents in parallel wires flow oppositely?
The wires repel due to opposing magnetic fields.
201. What is the force per unit length between parallel wires?
F/L
202. What is the force if Iâ
203. What is the use of a magnetic field in a loudspeaker?
It vibrates a coil to produce sound from current changes.
204. What is the role of a permanent magnet in a loudspeaker?
It provides a steady field for the coil to move in.
205. What is the effect of a stronger field in a generator?
It increases the induced EMF and power output.
206. What is the magnetic fieldâs role in an MRI machine?
Strong fields align atomic nuclei for imaging.
207. What is the effect of coil resistance in a motor?
Higher resistance reduces current and motor speed.
208. What is the induced EMF if N
209. What is the purpose of a magnetic brake?
It uses eddy currents to slow down moving objects.
210. What is the magnetic field due to a long straight wire at 0.2 m?
211. What is the field if I
212. What is the effect of doubling the turns in a solenoid?
213. What is the role of a commutator in a DC generator?
It converts AC in the coil to DC output.
214. What is the magnetic fieldâs effect on a charged particle?
It exerts a force perpendicular to velocity and field.
215. What is the force on a charge moving in a field?
216. What is the force if q
217. What is the path of a charged particle in a magnetic field?
It follows a circular path perpendicular to the field.
218. What is the radius of a charged particleâs path?
r
219. What is the use of a cyclotron?
It accelerates charged particles using magnetic fields.
220. What is the magnetic field in a vacuum?
It depends only on current, not medium (Îźâ).
221. What is the effect of an iron core in a solenoid?
It amplifies the magnetic field significantly.
222. What is the permeability of iron?
Itâs much higher than Îźâ, enhancing field strength.
223. What is the magnetic fieldâs role in a relay switch?
It pulls a contact to close or open a circuit.
224. What is the advantage of AC in transformers?
ACâs changing field enables voltage transformation.
225. What is the disadvantage of DC in transformers?
DCâs steady field doesnât induce voltage changes.
226. What is the magnetic field near a bar magnetâs equator?
Itâs weaker and opposite to the polesâ direction.
227. What is the effect of coil diameter in a solenoid?
Larger diameter reduces field strength per turn.
228. What is the torque if I
229. What is the use of a magnetic field in a hard disk?
It stores data by magnetizing tiny regions.
230. What is the effect of a shorted coil in a motor?
It reduces efficiency and may stop rotation.
231. What is the induced current if EMF
232. What is the magnetic fieldâs role in a maglev train?
It levitates and propels the train using repulsion.
233. What is the effect of a stronger magnet in a generator?
It increases the output voltage and power.
234. What is the role of slip rings in an AC generator?
They allow continuous AC output without reversal.
235. What is the frequency if a generator rotates at 3000 rpm, 2 poles?
f
236. What is the magnetic fieldâs effect on a compass near a wire?
The needle deflects due to the wireâs field.
237. What is the use of a solenoid in a car starter?
It engages the motor to crank the engine.
238. What is the power if V
239. What is the magnetic fieldâs role in a doorbell?
It moves an armature to strike the bell.
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