A conducting circular loop is placed in uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mms^-1. The induced emf in the loop when the radius is 2 cm is 

• 3.2 π μ V

• 4.8 π μ V

• 0.8 π μ V

• 0.8 π μ V

The electric field part of an electromagnetic wave in a medium is represented by
E_x = 0;

• moving along y direction with frequency 2π x 10⁶ Hz and wavelength 200 m.

• moving along x direction with frequency 10⁶ Hz and wavelength 200 m.

• moving along x direction with frequency 10⁶ Hz and wavelength 200 m
  
  

• moving along x direction with frequency 10⁶ Hz and wavelength 200 m
  
  

See the electrical circuit shown in this figure. Which of the following equations is a correct equation for it?

Power dissipated in an L-C-R series circuit connected to an AC source of emf is

In the phenomenon of electric discharge through gases at low pressure, the coloured glow in  the tube appears as a result of 

• excitation of electrons in the atoms

• a collision between the atoms of the gas

• a collision between the charged particle emitted from the cathode and the atoms of the gas

• a collision between the charged particle emitted from the cathode and the atoms of the gas

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

69.

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 %