Two glass plates are separated by water. If surface ension of water is 75 dyne/cm and area of each plate wetted by water is 8 cm² and the distance between the plates is 0.12 mm, then the force applied to separate the two plates is

• 10² dyne

• 10⁴ dyne

• 10⁵ dyne

• 10⁶ dyne

When a charged particle moving with velocity $\overrightarrow{\mathrm{v}}$is subjected to a magnetic field of $\overrightarrow{\mathrm{B}}$ induction , the force on it is non- zero. This implies that

• angle between $\overrightarrow{\mathrm{v}} \mathrm{and} \overrightarrow{\mathrm{B}}$ is necessarily 90^o

• angle between $\overrightarrow{\mathrm{v}} \mathrm{and} \overrightarrow{\mathrm{B}}$ can have any value other than 90^o

• angle between $\overrightarrow{\mathrm{v}} \mathrm{and} \overrightarrow{\mathrm{B}}$ can have any value other than 180^o

• angle between $\overrightarrow{\mathrm{v}} \mathrm{and} \overrightarrow{\mathrm{B}}$ is either zero or 180^o

When power is drawn from the secondary coil of the transformer, the dynamic resistance

• increases

• decreases

• remains unchanged

• changes erratically

What is not true for equipotential surface for uniform electric field?

• Equipotential surface is flat

• Equipotential surface is spherical

• Electric lines are perpendicular to equipotential surface 

• Work done is zero

A capacitor having capacitance 1 uF with air, is filled with two dielectrics as shown. How many times capacitance will increase

• 12

• 6

• 8/3

• 3

A galvanometer having a resistance of 8 Ω is shunted by a wire of resistance 2 Ω.1f the total current is 1 A, the part of it passing through the shunt will be

• 0.25 A

• 0.8 A

• 0.2 A

• 0.5 A

The north pole of a long horizontal bar magnet is being brought closer to a vertical conducting plane along the perpendicular direction. The direction of the induced current in the conducting plane will be

• horizontal

• vertical

• clockwise

• Anticlockwise

In refraction, light waves are bent on passing from one medium to the second medium, because, in the second medium

•  the frequency is different

• the coefficient of elasticity is different

• the speed is different

• the amplitude is smaller

Interference was observed in an interference chamber when air was present. Now, the chamber is evacuated and if the same light is used, a careful observation will show

• no interference

• interference with bright band

• interference with dark bands

• interference in which breadth of the fringe will be slightly increased 

30.

What maximum frequency can be reflected from ionosphere?

• 5 MHz

• 6 GHz

• 5 KHz

• 500 MHz