A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is , the net force on the remaining three arms of the loops is

• 3 

• -

• 
• 

A particle having a mass of 10^-2 kg carries a charge of 5 x 10^-8 C. The particle is given an initial horizontal velocity of 10⁵ ms^-1 in the presence of electric field and magnetic field. To keep the particle moving in a horizontal direction. it is necessary that

1)  should be perpendicular to the direction of velocity and  should be along the direction of velocity

2) Both  and  should be along the direction of velocity.

3) Both  and  are mutually perpendicular and perpendicular  to the direction of  velocity

4)  should be along the direction of velocity and  should be perpendicular to the direction of velocity.

• (1) and (3)

• (3) and (4)

• (2) and (3)

• (2) and (3)

A current loop consists of two identical semicircular parts each of radius R, one lying in the x-y plane and the other in x-z plane.  if the current in the loop is i. The resultant magnetic field due to the two semicircular parts at their common centre is

A wire of resistance 12 Ωm^-1 is bent to form a complete circle of radius 10 cm. The resistance between its two diametrically opposite point, A and B as shown in the figure, is

• 0.6 π Ω

•  3 π Ω

• 6 π Ω

• 6 π Ω

A student measures the terminal potential difference (V) of a cell (of emf and internal resistance r) as a function of the current (I) flowing through it. The slope and intercept of the graph between V and I, then respectively, equal

The magnetic force acting on a charged particle of charge -2 μC in a magnetic field of 2T acting in y direction, when the particle velocity is 

• 8N in -z direction

• 4N in z direction

• 8 N in y direction

• 8 N in y direction

A particle mass m, charge Q and kinetic energy T enter a transverse uniform magnetic field of induction. After 3 s the kinetic energy of the particle will be

• 3T

• 2T

• T

• T

A long solenoid has 500 turns. When a current of 2 A is passed through it, the resulting magnetic flux linked with each turn of the solenoid is 4 x 10^-3 Wb. The self -inductance of the solenoid is 

• 2.5 H

• 2.0 H

• 1.0 H

• 1.0 H

A galvanometer of resistance 50 Ω is connected to a battery of 3 V along with a resistance of 2950 Ω in series. A full-scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be

• 5050 Ω

• 5550 Ω

• 6050 Ω

• 6050 Ω

190.

Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What is the ratio of potential difference applied across them so that the magnetic field at their centres is the same?

• 3

• 4

• 6

• 6