# Objective Type Question or MCQ of Electrical Circuits and Magnetic Fields page-19

271.Ferrimagnetic materials are generally classified as

a) Conductors
b) Semiconductors
c) Dielectric
d) Insulators

Ans: (b)

272. Which of the material one will choose for transformer core if the transformer has to work at microwave frequency?

a) Supermalloy
b) Silicon
c) Ferrites
d) Iron

Ans: (c)

273. The magnetic materials exhibit the property of magnetization because of

a) Orbital motion electrons b) Spin of electrons
c) Spin of nucleus
d) Either of these
e) All of the above

Ans: (c)

274. A coil of 0.04 mH is carrying current of 1 A. If this current is reversed in 0.02 seconds, the induced emf in the coil will be

a) 0.16 V
b) 0.008 V
c) 0.004 V
d) 0.04 V

Ans: (c)

275. A coil wound on the iron core which carries current I. The self induced voltage in the coil is not affected by

a) Change of number of turns of coil
b) The resistance of magnetic path
c) Variation in voltage to the coil
d) Variation in coil current

Ans: (c)

276. How much energy will be stored in the magnetic field of coil which has self inductance of 10 mH and current of 20 A?

a) 1 joule
b) 10 joule
c) 2 joule
d) 20 joule

Ans: (c)

277. Which of the following statements is correct?

a) Inductance of the coil carrying a constant DC current will increase the current
b) The inductance of the coil carrying a constant DC current will not affect the current
c) The inductance of the coil carrying a constant DC current will decrease the current
d) The inductance of the coil carrying a constant Dc current will change the current into pulses

Ans: (b)

278. If the frequency of power supply is 60 Hz, what will be the period of one cycle?

a) 0.02 sec
b) 0.015 sec
c) 0.017 sec
d) 0.03 sec

Ans: (c)

279. If a sinusoidal wave has frequency of 50 Hz with 15 A rms current which of the following equation represents this wave

a) 15 sin⁡50 t
b) 30 sin⁡25 t
c) 42.42 sin⁡25 t
d) 21.21 sin⁡314 t

Ans: (d)

280. What will happen if the frequency of power supply in a pure capacitive circuit is doubled?

a) The current will be reduced to half
b) The current will also be doubled
c) The current will remain same
d) The current will increase by fourfold

Ans: (b)

281. The safest value of current the human body can carry more than 3 seconds is

a) 5 mA
b) 15 mA
c) 25 mA
d) 35 mA
e) 9 mA

Ans: (e)

282. Which of the following precaution will be taken first if a man suffers from electric shock?

a) Switch the power supply
b) Call the doctor
c) Make him lie on ground
d) Provide him glucose
e) Lie done on the ground and provide him artificial respiration

Ans: (e)

283. A transformer is designed to achieve 240 V AC 50 Hz supply with input of 3.3 kV, 50 Hz and output of 415 V 50 Hz. The secondary of the transformer will have

a) Three phase 3 wire system
b) Three phase 2 wire system
c) Thhee phase 6 wire system
d) Three phase 4 wire system

Ans: (d)

284. The hysteresis losses do not depend on

a) Volume of material
b) Magnetic field
c) Frequency
d) Either of them
e) None of these

Ans: (e)

285. For which of the following materials the net magnetic moment should be zero.

a) Ferromagnetic materials
b) Diamagnetic materials
c) Anti-ferrimagnetic materials
d) Anti-ferromagnetic materials

Ans: (d)

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