ELECTROMAGNETIC INDUCTION AND ALTERNATING CURRENTS

11 ) Free Physics Questions Online Mock Test Series By Cracktest

An electron moves along the line AB, which lies in the same plane as a circular loop of conducting wires as shown in figure. What will be the direction of current induced if any, in the loop ?

No current will be induced

The current will be clockwise

The current will be anticlockwise

The current will change direction as the electron passes by

View Solution

Answer :

passes by e is moving from left to right, the flux linked with the loop will first increase and decrease as electron passes by. So current will be first anticlockwise and change direction as electron passes by.

12 )

A circular loop of radius R carrying current I lies in X-Y plane with its centre at origin. The total magnetic flux through X-Y plane is......

Directly proportional to I

Directly proportional to R

Directly proportional to R^2

Zero

View Solution

Answer :

Field lines are shown as broken curves. From the figure, it is clear than

magnetic flux in X – Y plane will be zero.

13 )

Consider the situation shown in the figure. The wire AB is sliding on the fixed rails with a constant velocity v^➙. If the wire AB replaced by semi circular wire the magnitude of the induced current will.

Increases

decreased

Remain same

Depending on whether the semicircle bulge is towards the resistance or away from it

View Solution

Answer :

Rate of change of area with remain same even if wire is replaced by

semicircular wire,

∴ induced current will be same as earlier one as I = (e/R) & e i.e. induced

emf is function of area because

e = – N (dɸ / dt) = – N (d / dt) (AB cos wt).

14 )

When the number of turns in a coil is make four time without any change in length of the coil, its self inductance becomes....

Remain unchanged

Two times

Four times

Sixteen times

View Solution

Answer :

Self inductance = L = [(Nɸ) / ℓ] = [{μ₀N²A} / ℓ]

as turns are made four time L will change in proportion of N². Hence as

here N = 4.

L will becomes 4² = 16 times

15 )

Two similar circular loops carry equal currents in the same direction. On moving the coils further apart, the electric current will

Remain unchanged

Increasing in both

Increasing in one decreasing in other

Decreasing in both

View Solution

Answer :

Loops carry equal currents in same directions. Coil are moved further apart then current will increase in both.

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