The flux linked with a coil at any instant t is given by \(\Phi\)_B = 10t² − 50t + 250. The induced emf at t = 3s is

(a)

−190 V

(b)

−10 V

(c)

10 V

(d)

190 V

When the current changes from +2A to −2A in 0.05 s, an emf of 8 V is induced in a coil. The co-efficient of self-induction of the coil is

(a)

0.2H

(b)

0.4H

(c)

0.8H

(d)

0.1H

A step-down transformer reduces the supply voltage from 220 V to 11 V and increase the current from 6 A to 100 A. Then its efficiency is

(a)

1.2

(b)

0.83

(c)

0.12

(d)

0.9

In a series RL circuit, the resistance and inductive reactance are the same. Then the phase difference between the voltage and current in the circuit is

(a)

\(\frac{\pi}{4}\)

(b)

\(\frac{\pi}{2}\)

(c)

\(\frac{\pi}{6}\)

(d)

zero

An inductor 20 mH, a capacitor 50 μF and a resistor 40Ω are connected in series across a source of emf V = 10 sin 340 t. The power loss in AC circuit is

(a)

0.76 W

(b)

0.89 W

(c)

0.46 W

(d)

0.67 W

The unit henry can also be written as ______________.

(a)

VS A^-1

(b)

Wb A^-1

(c)

Ωs

(d)

all

The self-inductance of a straight conductor is ________________.

(a)

zero

(b)

infinity

(c)

very large

(d)

very small

An emf of 12V is induced when the current in the coil changes at the rate of 40 A S^-1. The coefficient of self induction of the coil is __________________.

(a)

0.3 H

(b)

0.003 H

(c)

30 H

(d)

4.8 H

An emf of 12V is induced when the current in the coil changes at the rate of 40 A S^-1. The coefficient of self-induction of the coil is _______________.

(a)

0.3 H

(b)

0.003 H

(c)

30 H

(d)

4.8 H

Transformer works on _____________.

(a)

AC only

(b)

DC only

(c)

both AC and DC

(d)

AC more effectively than DC

Faraday's law

(1)

Voltage and current are in phase

Ac circuit with resistor

(2)

Electromagnetic Induction

Ac circuit with inductor

(3)

Current leads voltage

Ac circult with capacitor

(4)

Voltage leads current

RLC circuit

(5)

Predominantly Inductive