Light with an average flux of ``20 {W}{cm^2}`` falls on a
non-reflecting surface at normal incidence having
surface area 20 ``cm^2``. The energy received by the
surface during time span of 1 minute is :
(1) ``10×10^3`` J
(2) ``12×10^3`` J
(3) ``24×10^3`` J
(4) ``48×10^3`` J

A spherical conductor of radius 10 cm has a charge
of ``3.2 \times 10^{-7}`` C distributed uniformly. What is
the magnitude of electric field at a point 15 cm
from the centre of the sphere ?
``(\frac{1}{4 \pi \epsilon_0} = 9 \times 10^9 \frac{N m^2}{C^2})``
(1) ``1.28×10^4 N/C``
(2) ``1.28×10^5 N/C``
(3) ``1.28×10^6 N/C``
(4) ``1.28×10^7 N/C``

In a certain region of space with volume 0.2 ``m^3``,
the electric potential is found to be 5 V throughout.
The magnitude of electric field in this region is :
(1) zero
(2) 0.5 N/C
(3) 1 N/C
(4) 5 N/C

The increase in the width of the depletion region
in a p-n junction diode is due to :
(1) forward bias only
(2) reverse bias only
(3) both forward bias and reverse bias
(4) increase in forward current

A 40 µF capacitor is connected to a 200 V, 50 Hz
ac supply. The rms value of the current in the
circuit is, nearly :
(1) 1.7 A
(2) 2.05 A
(3) 2.5 A
(4) 25.1 A

The mean free path for a gas, with molecular
diameter d and number density n can be expressed
as :
(1)
``\frac{1}{\sqrt{2} . n \pi d}``
(2)
``\frac{1}{\sqrt{2} .n \pi d^2}``
(3) ``\frac{1}{\sqrt{2} .n^2 \pi d^2}``
(4) ``\frac{1}{2 .n^2 d^2 π^2}``

For transistor action, which of the following
statements is correct ?
(1) Base, emitter and collector regions should
have same doping concentrations.
(2) Base, emitter and collector regions should
have same size.
(3) Both emitter junction as well as the collector
junction are forward biased.
(4) The base region must be very thin and lightly
doped.

Light of frequency 1.5 times the threshold
frequency is incident on a photosensitive material.
What will be the photoelectric current if the
frequency is halved and intensity is doubled ?
(1) doubled
(2) four times
(3) one-fourth
(4) zero

When a uranium isotope ``\ce{ {}^{235}_{92}U }`` is bombarded with
a neutron, it generates
``\ce{ {}^{89}_{36}Kr }``
, three neutrons and :
(1)
``\ce{ {}^{144}_{56}Ba }``
(2)
``\ce{ {}^{91}_{40}Zr }``
(3)
``\ce{ {}^{101}_{36}Kr }``
(4)
``\ce{ {}^{103}_{36}Kr }``

The energy required to break one bond in DNA is
``10^{-20}`` J. This value in eV is nearly :
(1) 6
(2) 0.6
(3) 0.06
(4) 0.006

Two bodies of mass 4 kg and 6 kg are tied to the
ends of a massless string. The string passes over
a pulley which is frictionless (see figure). The
acceleration of the system in terms of acceleration
due to gravity (g) is :

(1) g
(2) g/2
(3) g/5
(4) g/10

A wire of length L, area of cross section A is hanging
from a fixed support. The length of the wire
changes to ``L_1``
when mass M is suspended from its
free end. The expression for Young’s modulus is :
(1)
``\frac{MgL_1}{AL}``
(2)
``\frac{Mg(L_1 - L)}{AL}``
(3)
``\frac{MgL}{AL_1}``
(4)
``\frac{MgL}{A(L_1 - L)}``

The average thermal energy for a mono-atomic gas
is : (``k_B`` is Boltzmann constant and T, absolute
temperature)
(1)
``\frac12 k_B T ``
(2)
``\frac32 k_B T ``
(3)
``\frac52 k_B T ``
(4)
``\frac72 k_B T ``

Which of the following graph represents the
variation of resistivity (ρ) with temperature (T) for
copper ?
(1)
(2)
(3)
(4)

The color code of a resistance is given below :
The values of resistance and tolerance, respectively,
are :

(1) 470 kΩ, 5%
(2) 47 kΩ, 10%
(3) 4.7 kΩ, 5%
(4) 470 Ω, 5%