Electromagnetic Induction

A cell can be balanced against 110 cm and 100 cm of potentiometer wire, respectively with and without being short-circuited through a resistance of 10 Ω. Its internal resistance is

• 1.0 Ω

• 0.5 Ω

• 2.0 Ω

• 2.0 Ω

A circular disc of radius 0.2 m is placed in a uniform magnetic field of induction in such a way that its axis makes an angle of 60^o with. The magnetic flux linked with the disc is 

• 0.02 Wb

• 0.06 Wb

• 0.05 Wb

• 0.05 Wb

What is the value of inductance L for which the current is a maximum in a series LCR circuit with C =10μ F and ω = 1000 s^-1

• 100 mH

• 1 mH

• cannot bec calculated unless R is known

• cannot bec calculated unless R is known

Under the influence of a uniform magnetic field. a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion.

• depends on v and not on R

• depends on both R and v

• is independent of both R and v

• is independent of both R and v

A transforner is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately:

• 30%

• 50 %

• 90 %

• 90 %

When a charged particle moving with velocity  is subjected to a magnetic field of induction , the force on it is non-zero. This implies that

• angle between  is necessarily 

• angle between  can have any value other than 

• angle between  can have any value othe than zero and 

• angle between  can have any value othe than zero and 

Two coils of self-inductances 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is

• 10 mH

• 6 mH

• 4 mH

• 4 mH

The magnetic potential energy stored in a certain inductor is 25 mJ, when the current in the inductor is 60 mA. This inductor is of inductance

• 0.138 H

• 138.88 H

• 13.89

• 1.389 H

If the flux associated with a coil varies at the rate of 1wb/min the induced emf is

• zero

• 6oV

• $\frac{1}{60}\mathrm{V}$

• 1V

A circular coil of mean radius of 7 cm and having 4000 turns is rotated at the rate of 1800 revolutions per minute in the earth's magnetic field (B=0.5 gauss), the emf induced in coil will be

• 1.158 V

• 0.58 V

• 0.29 V

• 5.8 V