Eight mercury droplets having a radius of 1 mm and charge of 0.066 PC each merge to form one droplet. Its potential is _____________

(a)

2.4 V

(b)

1.2 V

(c)

3.6 V

(d)

4.8 V

The potential due to a single point charge falls as

(a)

\(\frac { 1 }{ { r }^{ 2 } } \)

(b)

\(\frac { 1 }{ { r }^{ 3 } } \)

(c)

\(\frac { 1 }{ { r }^{ } } \)

(d)

-\(\frac { 1 }{ { r }^{ } } \)

The emf of a battery is 3 volts and internal resistance 0.125 \(\Omega \) . The difference of potential at the terminal of battery when connected across an external resistance of 1 \(\Omega \) is ______________.

(a)

1.67 V

(b)

0.67 V

(c)

2.67 V

(d)

3.67 V

If a current I is flowing in a straight wire parallel to the x-axis and magnetic field is in the y-axis then the wire experiences in _________________.

(a)

in Z-direction

(b)

in Y- direction

(c)

no force

(d)

in X- diection

The Q factor of an a.c circuit containing a resistance R, inductance L and capacitor C is ________________.

(a)

\(Q=\frac { 1 }{ \sqrt { LC } } \)

(b)

\(Q=\frac { 1 }{ R } \sqrt { \frac { C }{ L } } \)

(c)

\(Q=\frac { 1 }{ R } \sqrt { \frac { L }{ C } } \)

(d)

\(Q=\frac { 1 }{ \sqrt { LR } } \)

The existence of E.M. waves was confirmed experimentally by __________________.

(a)

Hertz

(b)

Maxwell

(c)

Huygens

(d)

Planck

Two plane mirrors are at right angles to each other. A man stands between them and combs hair with his right hand. In how many of the images will he be seen using his right-hand __________.

(a)

None

(b)

1

(c)

2

(d)

3

A plane mirror is placed at the bottom of the tank containing a liquid of refractive index J.1.P is a small object at a height h above the mirror, an observer O-vertically above P outside the liquid. See p and its image in the mirror. The apparent distance between these two will be ____________.

(a)

\(2\mu h\)

(b)

\(\cfrac { 2h }{ \mu } \)

(c)

\(\cfrac { 2h }{ \mu -1 } \)

(d)

\(h\left( 1+\cfrac { 1 }{ \mu } \right) \)

The anode plate in an experiment on photoelectric effect is kept vertically above the emitter plate. Light source is put on. An electric field is switched on which has vertically downward direction.

(a)

The photo current will increase

(b)

The kinetic energy of the electrons will increase

(c)

The stopping potential will decrease

(d)

The transhold wavelength will increase

An oil drop carrying a charge q has a mass of m kg. It is falling freely in the air with terminal speed v. The electric field required to make the drop move upwards with the same speed is ______________.

(a)

\(\frac{mg}{q}\)

(b)

\(\frac{2mg}{q}\)

(c)

\(\frac{mgv}{q^2}\)

(d)

\(\frac{2mgv}{q}\)