The figure shows tow parallel equipotential surface A and B kept at a small distance 'r' a part from each other. A point change of Q coulomb is taken from the surface A to B. The amount of net work done will be 

(a)

\(W=\frac { -1 }{ 4\pi { \varepsilon }_{ 0 }r } \frac { q }{ r } \)

(b)

\(W=\frac { 1 }{ 4\pi { \varepsilon }_{ 0 }r } \frac { q }{ r } \)

(c)

\(W=\frac { -1 }{ 4\pi { \varepsilon }_{ 0 }r } \frac { q }{ r^2 } \)

(d)

zero

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

What will happen if two conducting spheres are separately charged and then brought in contact?

(a)

Total charge on the two spheres is conserved

(b)

The total energy is conserved

(c)

Both charge and energy are conserved

(d)

The final potential is the mean of the original potentials.

Temperature co-effieient of resistance for metals is ______________.

(a)

constant

(b)

positive

(c)

zero

(d)

negative

In an electrical arrangement as shown the equivalent resistance between X and Y will be

(a)

\(158.75\Omega \)

(b)

\(118.75\Omega \)

(c)

\(218.75\Omega \)

(d)

\(318.75\Omega \)

Conductor which obey ohm's law are called ______________.

(a)

dielectrics

(b)

superconductors

(c)

ohmic conductors

(d)

semiconductors

A long straight conductor carrying a current lies along the axis of a ring. The conductor will exert a force on the ring if _______________.

(a)

carries a current

(b)

has uniformly distributed charge

(c)

has non-uniformly distributed

(d)

none of the above

Ampere's circuital law is another form of ____________________.

(a)

Tangent law

(b)

Biot-Savart law

(c)

Ampere's Swimming rule

(d)

End rule

Force on unit length of two parallel wires carrying equal current kept apart by 3m in air is 2 x10^-7 N, then the current in each wire is ______

(a)

1A

(b)

3A

(c)

\(\sqrt { 3 } \)A

(d)

\(\sqrt { 2 } \)A

The unit of Galvanometer constant is ________

(a)

Am^-1

(b)

A rad^-1

(c)

AC^-1

(d)

As^-1

Transformer works on _____________.

(a)

AC only

(b)

DC only

(c)

both AC and DC

(d)

AC more effectively than DC

The property of a coil which enables to produce an opposite induced emf in it when the current in the coil changes is called _______________

(a)

electromagnetism

(b)

self - induction

(c)

mutual induction

(d)

parallel- induction

A magnetic field is produced by ____________.

(a)

a changing electric field

(b)

a moving charge

(c)

both of them

(d)

none of them

_________ emission spectrum is used to identify the gas used.

(a)

Continuous

(b)

Line

(c)

Band

(d)

Solid

An object is at a distance of 0.5 in front of a plane mirror. Distance between the object and image is ___________.

(a)

0.5 m

(b)

1m

(c)

7

(d)

8

A point source of light B is placed at a distance L in front of the center of a mirror of width d hung vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance of 2 L front it as shown. The greatest distance over which he can see the image of the light source in the mirror is ___________.

(a)

d/2

(b)

d

(c)

2d

(d)

3d

Under which of the following conditions will a convex mirror of focal length f produce an image that is erect diminished and virtual _____________.

(a)

only when 2f > u >f

(b)

only when u =f

(c)

only when u < f

(d)

always

When the intensity of a light source is increased?

(a)

the number of photons emitted by the source in unit time increases

(b)

more energetic photons are emitted

(c)

faster photons are emitted

(d)

total energy of the photons emitted per unit time decreases.

Light frequency v falls on material of threshold frequency v_o, the maximum K.E of emitted electron is proportional to ____________.

(a)

v-v₀

(b)

v

(c)

\(\sqrt { v-{ v }_{ 0 } } \)

(d)

v₀

The particle which has zero mass but has energy is _____________.

(a)

electron

(b)

photon

(c)

proton

(d)

neutron

Below the threshold frequency, if the intensity of radiation is increased, the emission of photoelectrons _______

(a)

increases

(b)

decreases

(c)

is zero

(d)

is a constant

The resolving power of a microscope is limited by the ______ of the radiation used.

(a)

wavelength

(b)

intensity

(c)

amplitude

(d)

time of travel

Millikan's oil drop experiment established that is ____________.

(a)

electric charge depends on velocity

(b)

electric charge is quantised

(c)

electron has wave nature

(d)

electron has particle nature

The energy of the electron in the first orbit of hydrogen atom is -13.6 eV. Its potential energy is _______________.

(a)

-13.6 eV

(b)

13.6eV

(c)

-27.2 eV

(d)

27.2 eV

J.J. Thomson discovered ________

(a)

protons

(b)

neutrons

(c)

electrons

(d)

quarks