If voltage applied on a capacitor is increased from V to 2V, choose the correct conclusion.

(a)

Q remains the same, C is doubled

(b)

Q is doubled, C doubled

(c)

C remains same, Q doubled

(d)

Both Q and C remain same

Two charged bodies of charges +q, -3q are brought in contact and separated. The charges prossed by each body after separation.

(a)

-q,-q

(b)

+q,-2q

(c)

-q, +3q

(d)

q, q

A carbon resistor of (47 ± 4.7 ) k Ω to be marked with rings of different colours for its identification. The colour code sequence will be ______.

(a)

Yellow – Green – Violet – Gold

(b)

Yellow – Violet – Orange – Silver

(c)

Violet – Yellow – Orange – Silver

(d)

Green – Orange – Violet - Gold

The internal resistance of a 2.1 V cell which gives a current of 0.2 A through a resistance of 10 Ω is ______.

(a)

0.2 Ω

(b)

0.5 Ω

(c)

0.8 Ω

(d)

1.0 Ω

The temperature coefficient of resistance is positive__________.

(a)

for metals

(b)

for insulators

(c)

(a) and (b)

(d)

all the above

A flat dielectric disc of radius R carries an excess charge on its surface. The surface charge density is σ. The disc rotates about an axis perpendicular to its plane passing through the center with angular velocity ω. Find the magnitude of the torque on the disc if it is placed in a uniform magnetic field whose strength is B which is directed perpendicular to the axis of rotation.

(a)

\(\frac { 1 }{ 4 } \sigma \omega \pi BR\)

(b)

\(\frac { 1 }{ 2 } \sigma \omega \pi B{ R }^{ 2 }\)

(c)

\(\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 3 }\)

(d)

\(\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 4 }\)

An α-particle enters a magnetic field of 1T with a velocity 10⁶ m/s in a direction perpendicular to the field. The force on α-particle is _____________________.

(a)

1.6 x 10^-13N

(b)

6.4  x 10^-13N

(c)

4.8  x 10^-13N

(d)

3.2  x 10^-13N

In a transformer, eddy current loss is minimized by using ____________.

(a)

laminated core made of muemetal

(b)

laminated core made of stelloy

(c)

shell type core

(d)

thick copper wire

The relation between velocity of light, permeability and permittivity of free space in________.

(a)

\({ C }^{ 2 }=\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } } \)

(b)

\(C=\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } } \)

(c)

\({ \mu }_{ 0 }={ \varepsilon }_{ 0 }c\)

(d)

\({ \varepsilon }_{ 0 }={ \mu }_{ 0 }c\)

Radio frequency waves are produced by ______.

(a)

radioactive nuclei

(b)

radioactive nuclear reactions

(c)

accelerated charges

(d)

radio - carbon

________ radiations are used to study atomic structure.

(a)

UV

(b)

IR

(c)

X-rays

(d)

Gamma

A plane mirror produces a magnification of ____________.

(a)

-1

(b)

+ 1

(c)

Zero

(d)

Between 0 and + ∞

In an experiment of finding the focal length of a concave mirror, a graph is drawn between the magnitudes of u and V. the graph looks like _____________.

(a)

(b)

(c)

(d)

An object 5 cm tall is placed 1m from the concave spherical mirror which has a radius of curvature of 20 cm. The size of the image is _____________.

(a)

0.11 cm

(b)

0.50 cm

(c)

0.55 cm

(d)

0.60 cm

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.

Gases begin to conduct electricity at low pressure because ______________.

(a)

at low pressure gases turn to plasma

(b)

colliding electrons can acquire higher K.E due to increased mean free path leading to ionisation of atoms

(c)

atoms breakup into electrons and protons

(d)

the electrons in atoms can move freely at low pressure

The minimum potential given to the anode for which the photoelectric current becomes zero is called _______ potential.

(a)

cut-off

(b)

threshold

(c)

saturation

(d)

active

The anode of a simple photo emissive cell is _______

(a)

glass tube

(b)

quartz crystal

(c)

platinum wire

(d)

iron rod

______ are used to study virus and bacteria.

(a)

Lenses

(b)

Mirrors

(c)

Electron microscope

(d)

Telescopes

Force is the rate of change of ________

(a)

mass

(b)

acceleration

(c)

momentum

(d)

velocity

The wavelength of de-Broglie waves doesn't depend on ________

(a)

mass

(b)

velocity

(c)

momentum

(d)

change

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)

\({ r }_{ n }∝ { n }^{ 2 }\)

When hydrogen atom is in its first excited level, its radius is __________ of the Bohr radius.

(a)

twice

(b)

same

(c)

half

(d)

four times

Cathode rays are nothing but ____________

(a)

electrons

(b)

protons

(c)

neutrons

(d)

hydrogen atoms

A pure semiconductor behaves slightly as a conductor of _______________.

(a)

low temperature

(b)

high temperature

(c)

room temperature

(d)

zero degree