An electric field \(\vec { E } =10x\hat { i } \) exists in a certain region of space. Then the potential difference V = V_o – V_A, where V_o is the potential at the origin and V_A is the potential at x = 2 m is _____.

(a)

10 V

(b)

-20 V

(c)

+20 V

(d)

-10 V

Charge per unit volume is called _____________

(a)

Linear charge density (λ)

(b)

Surface charge density (σ)

(c)

Volume charge density (ρ)

(d)

Electric flux

The negative gradient of potential is

(a)

torque

(b)

electric current

(c)

electric field intensity

(d)

electric force

A charge Q μ C is placed at the center of a cube. The flux coming out from any surface will be

(a)

\(\frac { Q }{ { 24\varepsilon }_{ 0 } } \)

(b)

\(\\ \frac { Q }{ { 8\varepsilon }_{ 0 } } \)

(c)

\(\frac { Q }{ { 6\varepsilon }_{ 0 } } \times { 10 }^{ -6 }\)

(d)

\(\frac { Q }{ { 6\varepsilon }_{ 0 } } \times { 10 }^{ -3 }\)

Surface density of charge on a sphere of radius R in terms of electric intensity E at a distance r in free space is

(a)

\({ \varepsilon }_{ 0 }E{ \left( \frac { R }{ r } \right) }^{ 2 }\)

(b)

\(\frac { { \varepsilon }_{ 0 }ER }{ { r }^{ 2 } } \)

(c)

\({ \varepsilon }_{ 0 }E{ \left( \frac { r }{ R } \right) }^{ 2 }\)

(d)

\({ e }_{ 0 }E\frac { r }{ { R }^{ 2 } } \)

Gauss law is another form of ________.

(a)

Newton's law

(b)

Kepler's law

(c)

Ohm's law

(d)

Coulomb's law

Two wires of A and B with circular cross section made up of the same material with equal lengths. Suppose R_A = 3 R_B, then what is the ratio of radius of wire A to that of B?

(a)

3

(b)

\(\sqrt3\)

(c)

\(\frac{1}{\sqrt3}\)

(d)

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

Kirchhoff's I law is a consequence of__________

(a)

law of conservation of energy

(b)

law of conservation of charges

(c)

law of conservation of currents

(d)

law of conservation of voltages

Three wires of equal lengths are bent in the form of loops. One of the loops is circle, another is a semi-circle and the third one is a square. They are placed in a uniform magnetic field and same electric current is passed through them. Which of the following loop configuration will experience greater torque?

(a)

Circle

(b)

Semi-circle

(c)

Square

(d)

All of them

Lorentz force generally refers to force experienced by a charge due to combined action of _________________.

(a)

magnetic fields

(b)

electric fields

(c)

electric, magnetic & gravitational fields

(d)

electric and magnetic fields

In an electrical circuit, R, L, C, and AC voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and current in the circuit is \(\frac{\pi}{3}\). Instead, if C is removed from the circuit, the phase difference is again \(\frac{\pi}{3}\). The power factor of the circuit is

(a)

1/2

(b)

1/\(\sqrt2\)

(c)

1

(d)

\(\sqrt3\)/2

Which current- time graph represents the steady movement of short magnet through a coil XY?

(a)

(b)

(c)

(d)

Which of the following is NOT true for electromagnetic waves?

(a)

it transport energy

(b)

it transport momentum

(c)

it transport angular momentum

(d)

in vacuum, it travels with different speeds which depend on their frequency

A magnetic field is produced by ____________.

(a)

a changing electric field

(b)

a moving charge

(c)

both of them

(d)

none of them

A ray of light travelling in a transparent medium of refractive index n falls, on a surface separating the medium from air at an angle of incidents of 45^o . The ray can undergo total internal reflection for the following n, ______.

(a)

n = 1.25

(b)

n = 1.33

(c)

n = 1.4

(d)

n = 1.5

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

In photoelectric emission, a radiation whose frequency is 4 times threshold frequency of a certain metal is incident on the metal. Then the maximum possible velocity of the emitted electron will be _____.

(a)

\(\sqrt { \frac { { hv }_{ o } }{ m } } \)

(b)

\(\sqrt { \frac { { 6hv }_{ o } }{ m } } \)

(c)

\(2\sqrt { \frac { { hv }_{ o } }{ m } } \)

(d)

\(\sqrt { \frac { { hv }_{ o } }{2m } } \)

Two photons each of energy 2.5 eV are simultaneously incident on the metal surface. If the work function of the metal is 4.5 eV then from the surface of the metal ______________.

(a)

one electron will be emitted

(b)

two electrons will be emitted

(c)

more than two electrons will be emitted

(d)

not a single electron will be emitted

Electron microscope operates in ______ media.

(a)

UV

(b)

X-ray

(c)

complete vacuum

(d)

air

Atomic number of H-like atom with ionization potential 122.4 V for n = 1 is _____.

(a)

1

(b)

2

(c)

3

(d)

4

The electric potential of an electron is given by \(V={ V }_{ 0 } \ In\left( \frac { r }{ { r }_{ 0 } } \right) \), where r₀ is a constant. If Bohr atom model is valid, then variation of radius of n^th orbit r_n with the principal quantum number n is _____.

(a)

\({ r }_{ n }∝ \frac { 1 }{ n } \)

(b)

\({ r }_{ n }∝ n\)

(c)

\({ r }_{ n }∝\frac { 1 }{ { n }^{ 2 } } \)

(d)

\({ r }_{ n }∝ { n }^{ 2 }\)

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

Output characteristics of an NPN, transistor in CE mode is drawn between ___________

(a)

I_C and V_BE

(b)

I_E and V_CE

(c)

I_B and V_CE

(d)

I_C and V_CE

The internationally accepted frequency deviation for the purpose of FM broadcasts ____________.

(a)

75 kHz

(b)

68 kHz

(c)

80 kHz

(d)

70 kHz

Optical fiber communication is generally preferred over general communication system because ____________.

(a)

it has signal security

(b)

it is more efficient

(c)

it cannot be jammed as easily as radio waves

(d)

all of the above