Physics Test 110

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Physics Test 110

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Weekly Quiz Competition

Question 1
4 / -1

200 MeV of energy may be obtained per fission of U²³⁵. A reactor is generating 1000 kW of power. The rate of nuclear fission in the reactor is :-

A
1000

B
2 × 10⁸

C
3.125 × 10¹⁶

D
931

Solution

Power = 1000 kW = 10⁶ J/s

Rate of nuclear fission

= 3.125 × 10¹⁶.
Question 2
4 / -1

In the following figure, the charge on each condenser in the steady state will be :-

A
3 μC

B
6 μC

C
9 μC

D
12 μC

Solution

In steady state current flows through 4Ω resistance only and is i = 10 / (4+1) = 2amp . Potential difference across 4Ω resistance is V = 2 × 4 = 8 volt

Hence, potential difference across each capacitor is 4V.

So charge on each capacitor Q = 3 × 4 = 12μC.
Question 3
4 / -1

The horizontal component of the earth's magnetic field at a place is 3 × 10^–4T and the dip is tan^–1(4/3). A metal rod of length 0.25 m placed in the north-south position and is moved at a constant speed of 10 cm/s towards the east. The emf induced in the rod will be :-

A
Zero

B
1μV

C
5μV

D
10μV

Solution

Rod is moving towards east, so induced emf across it's end will be e = B_vvl = (B_H tan ϕ)vl
∴ e = 3 × 10^–4× 4/3 × (10 × 10^–2) × 0.25

= 10^–5V = 10μV
Question 4
4 / -1

In which of the following circuit is the current maximum just after the switch S is closed :-

A
(i)

B
(ii)

C
(iii)

D
Both (ii) and (iii)

Solution

At t = 0 current through L is zero so it acts as open circuit. The given figures can be redrawn as follow.
Question 5
4 / -1

The potential difference V across and the current I flowing through an instrument in an AC circuit are given by : V = 5 cos ωt volt, I = 2 sin ωt Amp. The power dissipated in the instrument is :-

A
Zero

B
5 watt

C
10 watt

D
2.5 watt

Solution

P_av = v_rms I_rms cos ϕ

Here ϕ = 90° so P_av = 0
Question 6
4 / -1

Two parallel wires A and B carries 10A and 5A of currents in same direction respectively. Wire ‘A’ is infinite long and length of wire ‘B’ is 2m. Magnetic force on wire ‘B’, which is at 10 cm apart from wire ‘A’ is :-

A
2 × 10^–3 N, Attraction

B
2 × 10^–4 N, Repulsion

C
2 × 10^–3 N, Repulsion

D
2 × 10^–4 N, Attraction
Question 7
4 / -1

White light is used to illuminate the two slits in a Young's double slit experiment. The separation between slits is b and the screen is at a distance d (>>b) from the slits. At a point on the screen directly infront of one of the slits, certain wavelengths are missing. Some of these missing wavelengths are :-

A
λ = b²/d²

B
λ = 2b²/d

C
λ = b²/3d

D
λ = 2b²/3d

Solution
Question 8
4 / -1

A diverging beam of light from a point source S having divergence angle α, falls symmetrically on a glass slab as shown. The angles of incidence of the two extreme rays are equal. If the thickness of the glass slab is t and the refractive index n, then the divergence angle of the emergent beam is

A
zero

B
α

C
sin^–1(1/n)

D
2sin^–1(1/n)

Solution

Glass slab produces zero deviation, so angle of divergence does not change.
Question 9
4 / -1

If the intensity of sound is increased by a factor of 30, by how many decibels in the sound level increased :-

A
14.77 dB

B
14.50 dB

C
14.0 dB

D
None

Solution
Question 10
4 / -1

The frequency of a radar is 780 MHz. The frequency of the reflected wave from an aeroplane is increased by 2.6 KHz. The velocity of air plane is :-

A
0.25 km/s

B
0.5 km/s

C
1.0 km/s

D
2.0 km/s

Solution