41.

The length of a wire of a potentiometer is 100 cm, and the emf of its stand and cell is E volt. It is employed to measure the emf of a battery whose internal resistance is 0.52 Ω.1fthe balance point is obtained at l= 30 cm from the positive end, the emf of the battery is

• $\frac{30\mathrm{E}}{100.5}$

• $\frac{30\mathrm{E}}{100 - 0.5}$

• $\frac{30 (\mathrm{E} - 0.5\mathrm{i})}{100},\mathrm{where} \mathrm{i} \mathrm{is} \mathrm{the} \mathrm{current} \mathrm{in} \mathrm{the} \mathrm{potentiometer} \mathrm{wire}$

• $\frac{30\mathrm{E}}{100}$

The magnetic lines of force inside a bar magnet

• are from north-pole to south-pole of the magnet

• do not exist

• depend upon the area of cross-section of the bar magnet

• are from south-pole to north-pole of the magnet

Curie temperature is the temperature above which

• a ferromagnetic material becomes paramagnetic

• a paramagnetic material becomes diamagnetic

• a ferromagnetic material becomes diamagnetic

• a paramagnetic material becomes ferromagnetic

A particle of mass M and charge Q moving with velocity $\overrightarrow{\mathrm{v}}$ describes a circular path of radius R when subjected to a uniform transverse magnetic field of induction B. The work done by the field when the particle completes one full circle is.

• $\left(\frac{{\mathrm{Mv}}^2}{\mathrm{R}}\right)2\mathrm{\pi R}$

• zero

• BQ 2$\mathrm{\pi }$R

• BQv 2$\mathrm{\pi }$R

An L-C-R series circuit consists of a resistance of 10 Ω a capacitor of reactance 6.0 Ω and an inductor coil. The circuit is found to resonate when put across a 300 V, 100 Hz supply. The inductance of coil is (take $\mathrm{\pi }$ = 3)

• 0.1 H

• 0.01 H

• 0.2 H

• 0.02 H

Two coherent monochromatic light beams of intensities I and 9I are superimposed.The maximum and the minimum intensities of the resultant beams are

• 10 I and zero

• 10 I and 8 I

• 10 I and 4 I

• 16 I and 4 I

In a single slit diffraction pattern, the distance between the first minimum on the left and the first minimum on the right is 5 mm. The screen on which the diffraction pattern is displayed is at a distance of 80 cm from the slit. The, wavelength is 6000 A. The slit width (in mm) is about

• 0.576

• 0.348

• 0.192

• 0.096

When a ray is incident on a medium of refractive index n at Brewster's angle,it gets

• totally reflected

• totally absorbed

• circularly polarised

• plane polarised

The energy gap between the valence band and the conduction band for a material is 6 eV. The material is

• an insulator

• a metal

• an intrinsic semiconductor

• a superconductor

An AC signal of 50 Hz frequency is input of a full wave rectifier using two diodes. The output frequency after full wave rectification is

• 25 Hz

• 50 Hz

• 100 Hz

• 200 Hz