To get maximum current in a resistance of 3 ohms, one can use n rows of m cells (connected in series) connected in parallel. If the total number of cells is 24 and the internal resistance of a cell is 0.5 ohms then

m= 12, n =2
m= 8, n = 3
m= 2, n = 12
m= 6, n = 4

Solution

The time constant of C–R circuit is

1/CR
C/R
C R
R/C

Which of the following has the mass closest in value to that of the positron? (1 a.m.u. = 931 MeV)

Proton
Electron
Photon
Neutrino

Solution

Positron is the antiparticle of electron.

The cold junction of a thermocouple is maintained at 10ºC.No thermo e.m.f. is developed when the hot junction is maintained at 530ºC. The neutral temperature is

260ºC
265ºC
270ºC
520ºC

Solution

Neutral temperature,

\(\theta _{n}=\frac{\theta _{i}+\theta _{0}}{2}=\frac{530+10}{2}\)=270º C.

An aeroplane flying at a constant speed releases a bomb.As the bomb moves away from the aeroplane, it will

always be vertically below the aeroplane only if the aeroplane was flying horizontally
always be vertically below the aeroplane only if the aeroplane was flying at an angle of 45° to the horizontal
always be vertically below the aeroplane
gradually fall behind the aeroplane if the aeroplane was flying horizontally.

Solution

Since horizontal component of the velocity of the bomb will be the same as the velocity of the aeroplane,therefore horizontal displacements remain the same at any instant of time.

In a p-type semiconductor the acceptor level is situated 60meV above the valence band. The maximum wavelength of light required to produce a hole will be

0.207 × 10^–5 m
2.07 × 10^–5 m
20.7 × 10^–5 m
2075 × 10^–5 m

Solution

A coil of self-inductance L is connected in series with a bulb Band an AC source. Brightness of the bulb decreases when

number of turns in the coil is reduced
a capacitance of reactance X_C = X_L is included in the same circuit
an iron rod is inserted in the coil
frequency of the AC source is decreased

Solution

The potential energy of a system increases if work is done

upon the system by anon conservative force
by the system against a conservative force
by the system against anonconservative force
upon the system by a conservative force

Solution

When work is done upon a system by a conservative force then its potential energy increases.

Two blocks of masses 10 kg and 4 kg are connected by a spring of negligible mass and placed on a friction less horizontal surface. An impulse gives a velocity of 14 m/s to the heavier block in the direction of the lighter block. The velocity of the centre of mass is

30 m/s
20 m/s
10 m/s
5 m/s

Solution

\(V_{c}=\frac{10\times 14+4\times 0}{10+4}\)= 10m/s ; since spring force is internal force.

gun is aimed at a horizontal target. It takes 21s for the bullet to reach the target. The bullet hits the target x metre below the aim. Then, x is equal to

^9.8⁄₄m
^9.8⁄₈m
9.8 m
19.6 m

Solution

With the increases of temperature of a black body the peak of the spectral energy distribution of the radiation shift towards lower wavelength. This is given by :

Kirchoff’s law
Wein’s displacement law
Stefan’s law
Rayleigh-Jeans law

Solution

According to Wein’s displacement law, λ T = const.

In Young’s double slit experiment, the slits are 2 mm apart and a reilluminated by photons of two wavelengths λ₁= 12000 Å and λ₂= 10000 Å. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ?

6 mm
4 mm
3 mm
8 mm

Solution

If the forward voltage in a semiconductor diode is changed from 0.5V to 0.7 V,then the forward current changes by 1.0 mA. The forward resistance of diode junction will be

100 Ω
120 Ω
200 Ω
240 Ω

Solution

The equation of trajectory of projectile is given by \(y=\frac{x}{\sqrt{3}}-\frac{gx^{2}}{20}\), where x and y are in metre.The maximum range of the projectile is

⁸⁄₃m
⁴⁄₃m
³⁄₄m
³⁄₈m

Solution

An equiconvex lens is cut into two halves along (i) XOX’and (ii) YOY’ as shown in the figure. Let f, f’, f” be the focal lengths of the complete lens, of each half in case (i), and of each half in case (ii), respectively

Choose the correct statement from the following

f ' = 2f, f '' = 2f
f' = f, f '' = 2f
f' = 2f, f ''= f
f ' =f, f '' =f

Solution

UnAttempted

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