Light with an average flux of `` 20\,\Omega/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 :
(A) `` 10 \times 10^3J ``
(B) `` 12 \times 10^3J ``
(C) `` 24 \times 10^3J ``
(D) `` 48 \times 10^3J ``

A spherical conductor of radius 10cm 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_o} = 9 \times 10^9 Nm^2/C^2) ``
(A) `` 1.28 \times 10^4\,N/C ``
(B) `` 1.28 \times 10^5\,N/C ``
(C) `` 1.28 \times 10^6\,N/C ``
(D) `` 1.28 \times 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:
(A)zero
(B)0.5 N/C
(C)1 N/C
(D)5 N/C

The increase in the width of the depletion region in a p-n junction diode is due to :
(A)forward bias only
(B)reverse bias only
(C)both forward bias and reverse bias
(D)increase in forward current

A `` 40\, \mu\,F `` capacitor is connected to a `` 200\,V `` , `` 50\,Hz `` ac supply. The rms value of the current in the circuit is, nearly :
(A)1. 7 A
(B)2. 05 A
(C)2. 5 A
(D)25. 1 A

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

For transistor action, which of the following statements is correct ?
(A)Base, emitter and collector regions should have same doping concentrations.
(B)Base, emitter and collector regions should have same size.
(C)Both emitter junction as well as the collector junction are forward biased.
(D)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?
(A)doubled
(B)four times
(C)one-fourth
(D)zero

When a uranium isotope `` ^{235}_92 U `` is bombarded with a neutron, it generates `` ^{89}_{36} Kr `` , three neutrons and :
(A) `` ^{144}_{56} Ba ``
(B) `` ^{91}_{40} Zr ``
(C) `` ^{101}_{36} Kr ``
(D) `` ^{103}_{36} Kr ``

The energy required to break one bond in DNA is `` 10^{-20}J `` . This value in eV is nearly
(A)6
(B)0.6
(C)0.06
(D)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 :
(A)g
(B)g/2
(C)g/5
(D)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:
(A) `` \frac {MgL_1}{AL} ``
(B) `` \frac {Mg(L_1-L)}{AL} ``
(C) `` \frac {MgL}{AL_1} ``
(D) `` \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)
(A) `` \frac {1}{2} k_BT ``
(B) `` \frac {3}{2} k_BT ``
(C) `` \frac {5}{2} k_BT ``
(D) `` \frac {7}{2} k_BT ``

Which of the following graph represents the variation of resistivity `` (\rho) `` with temperature (T) for copper ?
(A)

(B)

(C)

(D)

The color code of a resistance is given below :
The values of resistance and tolerance, respectively, are :
(A)470 `` k\Omega,5\% ``
(B)47 `` k\Omega,10\% ``
(C)4.7 `` k\Omega,5\% ``
(D)470 `` \Omega,5\% ``