Two metallic spheres of radii 1 cm and 3 cm are given charges of –1 × 10^–2 C and 5 × 10^–2 C, respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is

2 × 10^–2C
3 × 10^–2 C
4 × 10^–2C
1 × 10^–2 C

Solution

A mass m is moving with a constant velocity along a line parallel to the x-axis, away from the origin. Its angular momentum with respect to the origin

is zero
remains constant
goes on increasing
goes on decreasing.

Solution

Angular momentum of mass m moving with a constant velocity about origin is

L = momentum × perpendicular distance of line of action of momentum from origin

L = mv × y

In the given condition mvy is a constant. There fore angular momentum is constant.

For an ideal gas graph is shown for three processes. Process1, 2 and 3 are respectively.

Isobaric, adiabatic, isochoric
Adiabatic, isobaric, isochoric
Isochoric, adiabatic, isobaric
Isochoric, isobaric, adiabatic

Solution

Isochoric proceess dV = 0

W = 0 proceess 1

Isobaric : W = PΔV = nRΔT

Adiabatic |W |= \(\frac{nR\Delta T}{\gamma -1}\) 0< γ– 1< 1 As work done in case of adiabatic process is more soprocess 3 is adiabatic and process 2 is isobaric.

From a steel wire of density ρ is suspended a brass block of density ρ_b. The extension of steel wire comes to e. If the brass block is now fully immersed in a liquid of density ρ_l,the extension becomes e’. The ratio ^e⁄_e’ will be

\(\frac{\rho b}{\rho _{b}-\rho _{\iota }}\)
\(\frac{\rho _{b}-\rho _{\iota }}{\rho _{b}}\)
\(\frac{\rho _{b}-\rho}{\rho _{l}- \rho }\)
\(\frac{\rho _{l}}{\rho _{b}- \rho_{l} }\)

Solution

Weights without and with liquid proportional to ρ_b and ρ_b– ρ_l.

Application of a forward bias to a p–n junction

widens the depletion zone.
increases the potential difference across the depletion zone
increases the number of donors on the n side.
increases the electric field in the depletion zone.

Directions : Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following

Statement-1 : Two stones are simultaneously projected fromlevel ground from same pointwith same speeds but different angles with horizontal. Both stones move in same verticalplane. Then the two stones may collide in mid air.

Statement-2 : For two stones projected simultaneously from same point with same speed at different angles with horizontal, their trajectories may intersect at some point.

(a)Statement -1 is false, Statement-2 is true
(b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1
(c)Statement -1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1
(d)Statement -1 is true, Statement-2 is false

Solution

(d)Statement -1 is true, Statement-2 is false

Coils in the resistance boxes are made from doubled up insulated wires

to cancel the effect of self induction
to nullify the heating effect
to nullify the Peltier effect
to reduce effective length of the wire

The ozone layer absorbs radiation of wavelengths

less than 3 × 10^–7 m
more than 3 × 10^–7 m
less than 3 × 10^–5 m
more than 3 × 10^–5 m

The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than 2480 nm is incident on it. The band gap (in eV) for the semiconductor is

Solution

300 J of work is done in sliding a 2 kg block up an inclined plane of height 10 m. Taking g = 10 m/s² work done against friction is

200 J
100 J
zero
1000 J

Solution

Total work done in sliding = work done against gravity+ work done against friction

or, 300J = mgh +work done against friction

⇒ Work done against friction

= 300J – 2 × 10 × 10J = 100 J

A copper disc of radius 0.1 m rotated about its centre with 10 revolutions per second in a uniform magnetic field of 0.1 tesla with its plane perpendicular to the field. The e.m.f.induced across the radius of disc is

^π⁄₁₀ volt
^2π⁄₁₀ volt
π × 10^-2 volt
2π × 10^-2 volt

Solution

A glass rod rubbed with silk is used to charge a gold leaf electroscope and the leaves are observed to diverge. The electroscope thus charged is exposed to X-rays for a short period. Then

the divergence of leaves will not be affected
the leaves will diverge further
the leaves will collapse
the leaves will melt

Solution

Charge on glass rod is positive, so charge on gold leaves will also be positive.Due to X-rays, more electrons from leaves will be emitted, so leaves becomes more positive and diverge further.

If the potential of a capacitor having capacity 6 μF is increased from 10 V to 20V, then increase in its energy will be

4 × 10^–4 J
4 × 10^–4 J
9 × 10^–4 J
12 × 10^–6 J

Solution

The position of final image formed by the given lens combination from the third lens will be at a distance of(f₁= + 10 cm, f₂= – 10 cm and f₃= + 30 cm).

15 cm
infinity
45 cm
30 cm

Solution

A plane mirror reflects a beam of light to form a real image.The incident beam is

parallel
convergent
divergent
any one of the above

Solution

Virtual object forms real image on a plane mirror, so rays convergent.

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