In the relation \(\phi \) = BA cos \(\theta \), \(\theta \) is angle........

1

(a)

which normal to surface area makes with the direction of magnetic field

(b)

which magnetic field makes with the surface

(c)

which is never constant

(d)

none of the above

The cause of induced e.m.f. is

1

(a)

magnetic flux

(b)

magnetic field

(c)

area

(d)

change in magnetic flux

Which one is not an application of eddy currents?

1

(a)

Magnetic brakes

(b)

speedometers

(c)

Induction furnace

(d)

Transformers

A wire of length 2m moves with a speed of 5m/s perpendicular to a magnetic field of induction 0.1 Wb/m². The e.m.f. induced in the wire is

1

(a)

1 V

(b)

10 V

(c)

5 V

(d)

2 V

Which of the following does not have the dimension of time?

1

(a)

RC

(b)

\(\frac { L }{ R } \)

(c)

\(\frac { R }{ L } \)

(d)

\(\sqrt { LC } \)

The resistance of a coil for direct current is 10ohm. When a.c. is sent through the same coil, its resistance would be

1

(a)

10\(\omega\)

(b)

> 10ohm

(c)

< 10ohm

(d)

cannot say

Q factor of resonance is given by

1

(a)

\(\frac { 1 }{ R } \sqrt { \frac { L }{ C } } \)

(b)

\(\frac { 1 }{ R } \sqrt { \frac { C }{ L } } \)

(c)

\(\frac { 1 }{ L } \sqrt { \frac { R }{ C } } \)

(d)

\(\frac { 1 }{ C } \sqrt { \frac { L }{ R } } \)

The frequency of a.c. generated depends on

1

(a)

speed of rotation of coil

(b)

amplitude of a.c

(c)

size of coil

(d)

all the above

In which of the following appliances, Fleming's right hand rule for direction of induced current is not applicable?

1

(a)

a.c.generator

(b)

d.c.generator

(c)

induction motor

(d)

transformer

A transformer is an electric device used for

1

(a)

producing direct current

(b)

producing alternating current

(c)

changing d.c. into a.c.

(d)

changing a.c. voltages

When is the magnetic flux crossing a given surface area held in a magnetic field maximum?

1

(a)

The magnetic flux is maximum when area is held perpendicular to the direction of magnetic field.

What is the dimensional formula of magnetic flux ?

1

(a)

\(\Phi =BAcos\Phi =(\frac { F }{ Il } )A=\frac { { MLT }^{ -2 } }{ AL } .{ L }^{ 2 }\)
\( =[{ ML }^{ 2 }{ T }^{ -2 }{ A }^{ -1 }]\)

What is the relation between weber and Maxwell ?

1

(a)

1 weber= \({ 10 }^{ 8 }\)Maxwell

A coil intercepts a magnetic flux of \(0.2\times { 10 }^{ -2 }\) Wb in 0.1 s. What is the emf induced in the coil ?

1

(a)

\(|e|=\frac { { d\Phi } }{ dt } =\frac { 0.2\times { 10 }^{ -2 } }{ 0.1 } =0.02\quad V\)

Does change in magnetic flux induce e.m.f. or current ?

1

(a)

Due to change in magnetic flux, e.m.f. is always induced, but induced current will flow only when tghe circuit is complete.