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Magnetism and Electromagnetic Induction MCQs — Physics (page 11)

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.

251. In a velocity selector, E = 20,000 V/m and B = 0.1 T are at right angles. The speed of particles that pass through undeflected is:

  1. 2000 m/s
  2. 2 10^5 m/s
  3. 4 10^5 m/s
  4. 1 10^5 m/s

Answer: B) 2 10^5 m/s

Explanation: qE = Bqv Rightarrow v = EB = 2 10^5 m/s. SLO P-09-E-34 · Understanding

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252. J. J. Thomson used crossed electric and magnetic fields to measure:

  1. the mass of the proton
  2. the speed of light
  3. the charge on a neutron
  4. the charge-to-mass ratio of the electron

Answer: D) the charge-to-mass ratio of the electron

Explanation: 1897 discovery of the electron. SLO P-09-E-34 · Understanding

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253. A magnet dropped through a copper tube falls slowly because:

  1. copper attracts magnets
  2. gravity is weaker in tubes
  3. air resistance is large
  4. induced currents in the tube create a field that opposes its motion

Answer: D) induced currents in the tube create a field that opposes its motion

Explanation: Lenz's law (eddy currents). SLO P-09-E-41 · Understanding

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254. Magnetic field lines outside a bar magnet go from:

  1. the middle outward
  2. north to south
  3. south to north
  4. nowhere

Answer: B) north to south

Explanation: And from S to N inside. SLO P-09-E-28 · Knowledge

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255. A flux density of 0.4 T passes perpendicularly through an area of 0.05 m^2. The magnetic flux is:

  1. 0.2 Wb
  2. 0.04 Wb
  3. 0.02 Wb
  4. 0.002 Wb

Answer: C) 0.02 Wb

Explanation: Phi = BA = 0.4 0.05 = 0.02 Wb. SLO P-09-E-39 · Application

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