  Easy Questions

## Electromagnetic Induction

- It is always better to start confident. Let's practice easy questions to serve the purpose
1
Problem on Magnetic Flux.
A circular coil of n turns is kept in a uniform magnetic field such that the plane of the coil is perpendicular to the field. The magnetic flux associated with the coil is now . Now the coil is opened and made into another circular coil of twice the radius of the previous coil and kept in the same field such that the plane of the coil is perpendicular to the field. The magnetic flux associated with this coil now is:
A
B
2
C
D
2
Induced emf in a closed loop.
An electron is moving in a circular orbit of radius R with an angular acceleration  At the center of the orbit is kept a conducting loop of radius  The e.m.f induced in the smaller loop due to the motion of the electron is:
A
zero, since charge on electron in constant
B
C
D
none of these
A conductor ABOCD moves along its bisector with a velocity of 1 ms through a perpendicular magnetic field of 1 Wbm, as shown in the figure. If all the four sides are of 1 m length each, then the induced emf between point A and D is :
A
zero
B
1.41 V
C
0.71 V
D
none of the above
3
Induced emf in a coil caused by varying flux due to magnetic field.
A square frame of side and a long straight wire carrying current are in the plane of the paper. Starting from close to the wire, the frame moves towards the right with a constant speed of (see figure). The e.m.f induced in the frame at the time the left arm is at  from the wire is :
A
B
C
D
4
Problems On Motional EMF.
What amount of power is generated in that resistance?
A
B
C
D
The force required to keep the rod moving with the speed of 3 ms (along + x-axis) is :(Take K = 4.5 N)
A
K
B
K
C
K
D
K
5
Problem on Mutual Inductance.
A long solenoid of length , cross section having turns has wound about its centre with a small coil of turns as shown in Fig. The mutual inductance of two circuits is:
A
B
C
D
6
Calculate mutual inductance of two inductors of different shapes.
The approximate formula expressing the formula of mutual inductance of two thin coaxial loops of the same radius when their centers are separated by a distance with is
A
B
C
D
7
Problem on combination of Inductor and Kirchhoff's Law
Consider the circuit shown in figure. (a) Find the current through the battery a long time after the switch is closed. (b) Suppose the switch is again opened at . What is the time constant of the discharging circuit?
8
Problem on Inductors
An inductance coil is connected to an source through a ,resistance in series. The source voltage, voltage across the coil and voltage across the resistance are found to be abd respectively. Therefore, the resistance of the coil is
A
B
C
D
9
Basic problem on dc and ac motors.
An electric motor connected to a    ac outlet does mechanical work at the rate of    (). (a) If the motor draws an    current of  , what is its effective resistance, relative to power transfer? (b) Is this the same as the resistance of the motors coils, as measured with an ohmmeter with the motor disconnected from the outlet?
10
Problem on transformer (EMF and current in AC generator).
Stepping up of voltage by a factor of 100,reduce the current by a factor of
A
10
B
100
C
leaves the current unchanged
D
increase the current by a factor of 100
11
Problem on DC Generator.
A neon lamp is connected to a voltage a.c. source. The voltage is gradually increased from zero volt. It is observed that the neon flashes at 50 V. The a.c. source is now replaced by a variable dc source and the experiment is repeated. The neon bulb will flash at
A
50V
B
70V
C
100V
D
35V