MCQs / Physics / Magnetism and Electromagnetic Induction

Magnetism and Electromagnetic Induction MCQs — Physics (page 10)

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.

226. A coil of 50 turns with its plane parallel to the field has a flux linkage of:

  1. BA
  2. 50BA
  3. BA50
  4. zero

Answer: D) zero

Explanation: No flux passes through. SLO P-09-E-40 · Understanding

Discuss this question

227. A relay uses an electromagnet to:

  1. measure temperature
  2. store charge
  3. produce light
  4. switch another circuit on or off

Answer: D) switch another circuit on or off

Explanation: Electromagnetic switch. SLO P-09-E-36 · Knowledge

Discuss this question

228. A solenoid with a soft-iron core is called:

  1. a permanent magnet
  2. an electromagnet
  3. a galvanometer
  4. a transformer

Answer: B) an electromagnet

Explanation: Switchable magnet. SLO P-09-E-36 · Knowledge

Discuss this question

229. The force on a current-carrying wire is zero when the wire is:

  1. at 45^circ to the field
  2. carrying a large current
  3. parallel to the magnetic field
  4. perpendicular to the field

Answer: C) parallel to the magnetic field

Explanation: sin 0^circ = 0. SLO P-09-E-29 · Understanding

Discuss this question

230. Ferrofluids react to:

  1. light only
  2. sound waves only
  3. the poles of a magnet (magnetic fields)
  4. electric charge only

Answer: C) the poles of a magnet (magnetic fields)

Explanation: They are magnetic fluids. SLO P-09-E-09 · Understanding

Discuss this question

231. The force on a current-carrying wire at 30^circ to a field is what fraction of the force when it is at 90^circ?

  1. 14
  2. 12
  3. 1
  4. 32

Answer: B) 12

Explanation: sin 30^circ = 0.5. SLO P-09-E-30 · Application

Discuss this question

232. A flux of 0.006 Wb passes perpendicularly through 0.02 m^2. The flux density is:

  1. 1.2 10^-4 T
  2. 3 T
  3. 0.03 T
  4. 0.3 T

Answer: D) 0.3 T

Explanation: B = PhiA = 0.3 T. SLO P-09-E-39 · Application

Discuss this question

233. Doubling both the speed of a moving conductor and the field strength makes the induced e.m.f.:

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

Answer: A) 4 times as large

Explanation: mathcalE = BLv. SLO P-09-E-42 · Application

Discuss this question

234. The direction of B in the definition is:

  1. random
  2. parallel to the force
  3. perpendicular to both the wire and the force
  4. parallel to the wire

Answer: C) perpendicular to both the wire and the force

Explanation: Fleming's rule geometry. SLO P-09-E-31 · Knowledge

Discuss this question

235. When the normal to a coil makes an angle theta with B, the flux is:

  1. Phi = BAcostheta
  2. Phi = BAsintheta
  3. Phi = BAtantheta
  4. Phi = BA

Answer: A) Phi = BAcostheta

Explanation: Component of area perpendicular to B. SLO P-09-E-38 · Knowledge

Discuss this question

236. A rod slides along rails in a field, and the induced current flows. By Lenz's law, the magnetic force on the rod:

  1. is zero
  2. helps its motion
  3. acts vertically upward always
  4. opposes its motion

Answer: D) opposes its motion

Explanation: Work must be done to keep it moving. SLO P-09-E-42 · Application

Discuss this question

237. A wire of length 2 m carries 10 A at 90^circ to a uniform magnetic field of 0.05 T. The force on it is:

  1. 2 N
  2. 3 N
  3. 1 N
  4. 0.5 N

Answer: C) 1 N

Explanation: F = BILsintheta = 0.05 10 2 sin 90^circ = 1 N. SLO P-09-E-30 · Application

Discuss this question

238. In a moving-coil loudspeaker, the cone vibrates because:

  1. sound pushes it
  2. the varying current in the coil experiences a varying force in the magnet's field
  3. air flows through it
  4. the magnet vibrates

Answer: B) the varying current in the coil experiences a varying force in the magnet's field

Explanation: Motor effect. SLO P-09-E-29 · Understanding

Discuss this question

239. A proton moves at 2 10^6 m/s perpendicular to a 0.5 T field. The radius of its circular path is (m = 1.67 10^-27 kg, q = 1.6 10^-19 C):

  1. 0.418 m
  2. 0.00418 m
  3. 0.0418 m
  4. 0.0835 m

Answer: C) 0.0418 m

Explanation: Bqv = mv^2r Rightarrow r = mvBq = 0.0418 m. SLO P-09-E-33 · Understanding

Discuss this question

240. The Earth's magnetic field protects us by:

  1. deflecting charged particles from the Sun (solar wind)
  2. causing tides
  3. stopping sunlight
  4. keeping the atmosphere warm

Answer: A) deflecting charged particles from the Sun (solar wind)

Explanation: Magnetosphere. SLO P-09-E-28 · Knowledge

Discuss this question

241. Inside a solenoid, the field lines run from:

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

Answer: C) the south pole end to the north pole end

Explanation: Closed loops, like a bar magnet. SLO P-09-E-35 · Application

Discuss this question

242. In Fleming's left-hand rule, the first finger points along the:

  1. current
  2. magnetic field
  3. voltage
  4. force (motion)

Answer: B) magnetic field

Explanation: First finger = Field. SLO P-09-E-30 · Application

Discuss this question

243. The speed selected does NOT depend on:

  1. the magnetic field
  2. the ratio E/B
  3. the electric field
  4. the charge or mass of the particle

Answer: D) the charge or mass of the particle

Explanation: v = E/B only. SLO P-09-E-34 · Understanding

Discuss this question

244. In Fleming's left-hand rule, the second finger points along the:

  1. current
  2. force
  3. field
  4. velocity of electrons

Answer: A) current

Explanation: seCond finger = Current (conventional). SLO P-09-E-30 · Application

Discuss this question

245. Placing a soft-iron core inside a solenoid:

  1. has no effect
  2. greatly increases the magnetic field
  3. reverses the field
  4. reduces the field

Answer: B) greatly increases the magnetic field

Explanation: Iron becomes magnetised and adds its own field. SLO P-09-E-36 · Knowledge

Discuss this question

246. Reversing both the current and the field:

  1. doubles the force
  2. reverses the force
  3. leaves the force direction unchanged
  4. removes the force

Answer: C) leaves the force direction unchanged

Explanation: Two reversals cancel. SLO P-09-E-29 · Understanding

Discuss this question

247. A seismometer is buried in a protective case resting on rock so that:

  1. it moves with the rock and records its vibrations
  2. it avoids all vibrations
  3. it stays warm
  4. it is invisible

Answer: A) it moves with the rock and records its vibrations

Explanation: Coupled to the ground. SLO P-09-E-43 · Application

Discuss this question

248. If the magnetic field is made stronger, the radius of the path:

  1. stays the same
  2. increases
  3. becomes infinite
  4. decreases

Answer: D) decreases

Explanation: r propto 1/B. SLO P-09-E-33 · Understanding

Discuss this question

249. A coil of area 0.25 m^2 is in a 0.2 T field; the field makes 90^circ with the normal to the coil. The flux through the coil is:

  1. 0 Wb
  2. 0.05 Wb
  3. 0.8 Wb
  4. 0.025 Wb

Answer: A) 0 Wb

Explanation: Phi = BAcostheta = 0.2 0.25 cos 90^circ = 0 Wb. SLO P-09-E-39 · Application

Discuss this question

250. Switching on a current in one coil makes a galvanometer connected to a nearby second coil:

  1. deflect briefly
  2. not deflect
  3. deflect steadily
  4. reverse permanently

Answer: A) deflect briefly

Explanation: Changing flux only at the switching moment. SLO P-09-E-41 · Understanding

Discuss this question

Previous Page 10 of 11 Next

Practise Magnetism and Electromagnetic Induction MCQs

More Physics chapters