MCQs / Physics / Magnetism and Electromagnetic Induction

Magnetism and Electromagnetic Induction MCQs — Physics (page 9)

255 multiple-choice questions on Magnetism and Electromagnetic Induction from Physics, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

201. A wire of length 0.5 m carries 4 A at 0^circ to a uniform magnetic field of 0.8 T. The force on it is:

  1. 1.6 N
  2. 0 N
  3. 6.4 N
  4. 0.8 N

Answer: B) 0 N

Explanation: F = BILsintheta = 0.8 4 0.5 sin 0^circ = 0 N. SLO P-09-E-30 · Application

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202. A ferrous material contains:

  1. copper
  2. iron
  3. plastic
  4. aluminium

Answer: B) iron

Explanation: Ferrous = iron-containing. SLO P-09-E-36 · Knowledge

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203. Magnetic flux linkage is:

  1. PhiN
  2. NPhi
  3. Phi + N
  4. Phi^N

Answer: B) NPhi

Explanation: Flux through each turn × number of turns. SLO P-09-E-40 · Understanding

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204. The direction of the field around a straight wire is given by:

  1. Lenz's law
  2. the right-hand grip rule
  3. Fleming's left-hand rule
  4. Snell's law

Answer: B) the right-hand grip rule

Explanation: Thumb along current, fingers curl with field. SLO P-09-E-35 · Application

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205. A coil's flux linkage increases at a steady rate. The induced e.m.f. is:

  1. constant
  2. decreasing
  3. increasing
  4. zero

Answer: A) constant

Explanation: Constant rate of change. SLO P-09-E-42 · Application

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206. The magnetic force on a moving charge does no work because:

  1. it is very small
  2. it is always perpendicular to the velocity
  3. the charge stops
  4. the field is uniform

Answer: B) it is always perpendicular to the velocity

Explanation: Speed (KE) stays constant. SLO P-09-E-32 · Application

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207. The field at the centre of a flat circular coil is:

  1. circular around the centre
  2. zero
  3. along the axis of the coil, perpendicular to its plane
  4. in the plane of the coil

Answer: C) along the axis of the coil, perpendicular to its plane

Explanation: Field lines pass straight through the centre. SLO P-09-E-35 · Application

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208. If only E is doubled, the selected speed:

  1. halves
  2. quadruples
  3. doubles
  4. stays the same

Answer: C) doubles

Explanation: v propto E. SLO P-09-E-34 · Understanding

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209. Using a coil with more turns (same motion) makes the induced e.m.f.:

  1. larger
  2. smaller
  3. zero
  4. the same

Answer: A) larger

Explanation: mathcalE propto N. SLO P-09-E-41 · Understanding

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210. If a charged particle enters a field at an angle (not 90°), its path is:

  1. a circle
  2. a parabola
  3. a helix (spiral)
  4. a straight line

Answer: C) a helix (spiral)

Explanation: Velocity component along B is unaffected. SLO P-09-E-33 · Understanding

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211. The core increases the field because:

  1. it carries extra current
  2. the magnetic domains in the iron line up with the solenoid's field
  3. it heats up
  4. it is charged

Answer: B) the magnetic domains in the iron line up with the solenoid's field

Explanation: Domain alignment. SLO P-09-E-36 · Knowledge

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212. Increasing the number of turns per metre of a solenoid (same current):

  1. increases the field inside
  2. has no effect
  3. makes the field zero
  4. decreases the field

Answer: A) increases the field inside

Explanation: B = mu0 nI. SLO P-09-E-35 · Application

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213. Reversing the current in a wire in a magnetic field:

  1. reverses the force
  2. does nothing
  3. makes the force zero
  4. doubles the force

Answer: A) reverses the force

Explanation: Direction depends on current direction. SLO P-09-E-29 · Understanding

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214. A wire of length 0.1 m carries 2 A at 30^circ to a uniform magnetic field of 0.5 T. The force on it is:

  1. 0.05 N
  2. 0.025 N
  3. 0.1 N
  4. 0.06 N

Answer: A) 0.05 N

Explanation: F = BILsintheta = 0.5 2 0.1 sin 30^circ = 0.05 N. SLO P-09-E-30 · Application

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215. A search coil measures field strength because its induced e.m.f. depends on the change of:

  1. its mass
  2. its resistance
  3. flux linkage
  4. its temperature

Answer: C) flux linkage

Explanation: Faraday's law. SLO P-09-E-40 · Understanding

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216. The discovery that currents feel forces in magnetic fields led to the invention of:

  1. the light bulb
  2. the telescope
  3. the electric motor
  4. the battery

Answer: C) the electric motor

Explanation: Faraday's motor, 1821. SLO P-09-E-29 · Understanding

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217. Rotating a coil from perpendicular to parallel with the field changes the flux from:

  1. BA to 0
  2. 0 to BA
  3. BA to 2BA
  4. it doesn't change

Answer: A) BA to 0

Explanation: cos 90^circ = 0. SLO P-09-E-38 · Knowledge

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218. The force on a stationary charge in a magnetic field is:

  1. infinite
  2. zero
  3. Bq
  4. Bqv

Answer: B) zero

Explanation: v = 0. SLO P-09-E-32 · Application

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219. If the current in both wires is doubled, the force between them becomes:

  1. 4 times as large
  2. unchanged
  3. 2 times as large
  4. half

Answer: A) 4 times as large

Explanation: F propto I1I2. SLO P-09-E-37 · Understanding

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220. The force on a current-carrying wire is maximum when the wire is:

  1. outside the field
  2. perpendicular to the magnetic field
  3. at 30^circ to the field
  4. parallel to the field

Answer: B) perpendicular to the magnetic field

Explanation: sin 90^circ = 1. SLO P-09-E-29 · Understanding

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221. The unit N = T C m s^-1 shows that 1 T equals:

  1. 1 N m
  2. 1 N s C^-1 m^-1
  3. 1 C m s^-1
  4. 1 N C^-1

Answer: B) 1 N s C^-1 m^-1

Explanation: From B = F/(qv). SLO P-09-E-32 · Application

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222. Two parallel wires with currents in the same direction are 5 cm apart. Moving them to 10 cm apart makes the attraction:

  1. double
  2. halve
  3. quarter
  4. unchanged

Answer: B) halve

Explanation: F propto 1/d. SLO P-09-E-37 · Understanding

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223. In the definition of B, the wire must be placed:

  1. parallel to the field
  2. outside the field
  3. at 45^circ
  4. at right angles to the field

Answer: D) at right angles to the field

Explanation: So that sintheta = 1. SLO P-09-E-31 · Knowledge

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224. A wire of length 0.25 m carries 3 A at 60^circ to a uniform magnetic field of 1.2 T. The force on it is:

  1. 0.39 N
  2. 1.56 N
  3. 0.9 N
  4. 0.779 N

Answer: D) 0.779 N

Explanation: F = BILsintheta = 1.2 3 0.25 sin 60^circ = 0.779 N. SLO P-09-E-30 · Application

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225. A coil of 40 turns and area 0.05 m^2 is perpendicular to a 0.6 T field. The flux linkage is:

  1. 0.03 Wb-turns
  2. 0.6 Wb-turns
  3. 1.2 Wb-turns
  4. 2.4 Wb-turns

Answer: C) 1.2 Wb-turns

Explanation: NPhi = NBA = 40 0.6 0.05 = 1.2 Wb-turns. SLO P-09-E-40 · Understanding

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