TEST 5

PPSC PHYSICS
ELECTRICITY AND MAGNETISM + MODERN PHYSICS
1) A point charge q placed at origin produces an electric field E at a point P which is on x-axis
at a distance of r from origin. If another charge q is placed at location 2r on x-axis, the net
field on same point is .
A) 2E B) Zero C) E/2 D) -E
2) Charge can be produced on an object by .
A) Electromagnetic induction B) Electrostatic induction
B) Friction D) All of these
3) A charge q placed at origin produces a potential V at a point which is at distance d from the
charge on x-axis. If another charge is placed at distance 3d/2 on x-axis, the net potential at
point P is .
A) –V C) 2V
B) 3V D) 4V
4) A hollow spherical conducting shell of radius R is charged by positive charge Q. The
potential at its surface is V. The potential inside the shell at its centre will be .
A) V/2 C) Zero
B) V/4 D) V
5) Two oppositely charged spherical shell of very small size are placed on a line. Field between
them is non-uniform but continuous. A thick conducting sheet of thickness d is placed
between them. The field now becomes .
A) Non-uniform and discontinuous C) Uniform but discontinuous
B) Uniform and continuous D) Remains unaltered
6) A metallic conductor retains excess charge .
A) On its surface C) No excess charge can be placed on conductors
B) Inside the body D) Either inside or outside
7) Electric field strength at point P(1,1,1) will be N/C if V(x,y) = (x2 + y2) V in a certain
region.
A) 1.1 C) Zero
B) 2.8 D) 2
8) A point charge q is placed inside a spherical shell of radius R charged to charge Q. The force
on the point charge is proportional to .
2
A) Qq/R C) R
B) Qq D) Force is zero in this case
9) A solid three dimensional spherical distribution of charge is present with volume charge
density ρ and radius R. The electric field inside the spherical distribution is .
A) Proportional to ρ C) Always zero
B) Inversely proportional to ρ D) Proportional to ρ/r
10) A spherical capacitor of inner and outer radius a and 2a has capacitance F where a = 9
9
x 10 m.
A) 2 C) 0.5
B) 255 D) Zero
11) A cylindrical capacitor (unit length) of inner and outer radius R and eR will store a charge
of C when P.D. of 100 V is applied across its plates where e = 2.7182 (base of natural
logarithm).
A) 100πεo C) 200πεo
B) πεo/100 D) 2πεo
12) Between the plates of a parallel plate capacitor, the potential as we move from
positive to negative plate.
A) Increases linearly C) Decreases linearly
B) Remains constant D) Vanishes
13) The charging current reduces to of its maximum value when t = 2RC has elapsed.
A) 50 % C) 126 %
B) 63 % D) 14 %
14) If slope of charging curve for capacitor is greater, time constant is .
A) Intermediate C) Small
B) Zero D) Large
15) When a closed switch passing heavy current is opened quickly, spark jumps due to
.
A) Stored energy C) Environmental pressure
 B) Mismatching of metallic contacts D) Peltier effect
16) Inside a long solenoidal coil, field is B. The field strength at its corners is approximately .
A) B C) B/2
B) Zero D) 2B
17) Magnetic field outside a solenoid does not depend upon .
A) Medium around the coil C) Current inside the solenoid
B) Number of turns of the coil D) Distance from axis of the coil
18) Magnetic energy stored inside a coil depends on .
A) Thickness of wire of coil C) Square of current
B) Square of inductance D) Reciprocal of inductance
19) A toroidal coil of inner radius a and outer radius b carries current I and N turns. The magnetic
field at the centre of the toroid is .
A) μoNI/a C) Zero
B) μoNI/b D) μoNI/(a+b)
20) When switch is closed in a series RL circuit containing DC source, the induced emf is
initially.
A) Half of the maximum C) Maximum
B) Zero D) Minimum
21) An operator used in quantum mechanics is always .
A) Recursive C) Hermition
B) Regenerative D) Linear
22) When surface temperature of a star decreases to half, spectral radiancy should .
A) Decrease 4 times C) Decrease 16 times
B) Remain same D) Halve
23) A star radiates most energy in infrared region at 800 nm. Suddenly, fusion process starts
rapidly and temperature increases to double, the color of the star will turn .
A) Yellow C) Blue
B) Green D) Red
24) Quantization of energy at atomic level resolves the spectral radiancy of blackbody radiation
spectrum.
A) True for short wavelengths C) True
B) True for intermediate wavelengths D) True for longer wavelengths
25) The quantized energy steps are at macroscopic level.
A) Infinite C) Very small
B) Intermediate D) very large
26) Spectrum obtained due to Bremsstrahlung effect is .
A) Sharp C) Continuous
B) Band D) Discrete
27) Hydrogen alpha line in visible spectrum corresponds to wavelength of .
A) 364.6 nm C) 656 nm
B) 486 nm D) 410 nm
28) Series limit in Lyman series is .
A) 4/3RH C) 1/RH
B) RH/2 D) Zero
29) The emission series of hydrogen lying in microwave region is series.
A) Paschen C) Humphreys
B) Balmer D) Brackett
30) A photon of energy E is incident on a metal of work function ϕ, the maximum kinetic energy
of photoelectrons is K. When energy of incident photon increases to 2E, the maximum kinetic
energy of photoelectron increases to .
A) K/2 C) More than 2K
B) 2K D) Less than 2K
31) An ideal particle can only be represented by a wave packet of plane wave(s) in phase-space.
A) Two C) Infinite
B) Three D) One
32) A plane wave has .
A) Definite momentum and position C) Definite momentum, un-localized in space
B) Definite position only D) Definite energy and un-localized in time
33) A function which describes the wave-like properties of particles is called .
A) Operator C) Wavefunction
B) Commutator D) State variable
34) Wave nature of electrons was proved by .
 A) Max. Born C) G. P. Thomson
B) Maxwell D) J. J. Thomson
35) If accelerating potential of a charged particle is increased to 4 times, the de-Broglie wavelength
.
A) Quarters C) Halves
B) Quadruples D) Doubles
2
36) Energy of a classical particle of mass m is p +3m where p is its momentum. Its speed at a point
is when p=3.
A) 3 C) 6
B) 12 D) Zero
37) The de-Broglie waves are waves.
A) Probability C) Mechanical
B) Deterministic D) Electromagnetic
38) The frequency of k-alpha x-ray photon is directly proportional to .
A) Z C) √𝒁
2
B) Z D) 1/√𝑍
39) K-alpha x-ray photon is most energetic for target.
A) Silver C) Tungsten
B) Copper D) Same for all
40) The cutoff wavelength in a Coolidge tube when accelerating potential remains same
while target is changed.
A) Decreases C) Remains same
B) May increase or decrease D) Increases