Electrical Engineering Questions and Answers


81)

Faraday's law states that relative motion between a magnetic field and a coil induces a voltage across the coil.

Answer: Option A

 
82)

An induced voltage is produced as a result of a dc voltage.

Answer: Option B

Explanation:

Voltage is induced whenever there is change in flux with respect to time according to faradays law of electro magnetic induction.in case of dc,the voltage is constant with respect to time I.E there is no change of flux w.r.to time (e=-d@/dt=0) and hence the inductor acts as short circuit or frequency of dc is zero hence inductive reactance 2*pi*f*L=0 AND INDUCTOR ACTS AS SHORT CIRCUIT.
83)

XL is directly proportional to frequency and inductance.

Answer: Option A

Explanation:

XL=2(pi)fL

pi=22/7 or 3.14

pi and L constant

So, XL is proportional to f.
84)

The permeability of a core material is an indication of the ability of the material to establish a magnetic field.

Answer: Option A

Explanation:

The permeability directly relate to the fore of attraction it means to increase magnetic field we need a permeable material to enhance strength.
85)

When the current through an inductor is cut in half, the amount of energy stored in the electromagnetic field

Answer: Option A

Explanation:

Energy stored is 1/2 L I2.

If I is halved, energy stored gets reduced to 1/4 th.

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