Physics Test 223

Result

Physics Test 223

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Weekly Quiz Competition

Question 1
4 / -1

An X-ray tube produces a continuous spectrum of radiation with its shortest wavelength of 45 × 10⁻² Å. The maximum energy of a photon in the radiation in eV is (h =6.62 × 10⁻³⁴J s, c = 3 × 10⁸ m s⁻¹)

A
27,500

B
22,500

C
17,500

D
12,500

Solution
Question 2
4 / -1

On heating water, bubbles being formed at the bottom of the vessel detach and rise. Take the bubbles to be spheres of radius R and making a circular contact of radius r with the bottom of the vessel. If r < < R, and the surface tension of water is T, value of r just before bubbles detach is

(density of water is p_w)

A

B

C

D
None of these

Solution
Question 3
4 / -1

An air-tight cage with a parrot sitting in it is suspended from the spring balance. The parrot starts flying. The reading of the spring balance will

A
Increase

B
Decrease

C
Not change

D
Be zero

Solution

The system is closed. The weight of the parrot suppresses the base of the air cage with a weight equal to the weight of the parrot. These are internal forces. So there will be no change in the reading of the spring balance.
Question 4
4 / -1

A rod AD, consisting of three segments AB, BC and CD joined together, is hanging vertically from a fixed support at A. The lengths of the segments are respectively 0.1 m, 0.2 m and 0.15 m. The cross - section of the rod is uniform 10^-4 m². A weight of 10 kg is hung from D. Calculate the displacements of point D if Y_AB = 2.5 x 10¹⁰ N/m², Y_BC = 4 x 10¹⁰ N/m² and Y_CD = 1 x 10¹⁰ N/m². (Neglect the weight of the rod.)

A
23.5 x 10^-6 m

B
4.90 x 10^-6 m

C
14.7 x 10^-6 m

D
8.82 x 10^-6 m

Solution
Question 5
4 / -1

Variation of resistance of the conductor with temperature is as shown. Temperature coefficient of the conductor is

A
R₀/m

B
mR₀

C
m²R₀

D
m/R₀

Solution

R_t= R₀(1 + αΔT), where α is the temperature coefficient of the conductor.

⇒ R_t = R₀+ R₀αΔT

Slope of graph m = R₀α

∴ α = m/R₀
Question 6
4 / -1

Two point charges exert on each other a force F when they are placed r distance apart in air. When they are placed R distance apart in medium of dielectric constant K, they exert the same force. The distance R equals

A

B
r/K

C
rK

D
r√K

Solution

In vacuum, force between charges is F₁ while in medium is F₂
Question 7
4 / -1

In an adiabatic process, the pressure is increased by 2/3% and C_p/C_v= 3/2 for the gas. Then the volume decreases by about:

A
4/9%

B
2/3%

C
4%

D
9/4%

Solution
Question 8
4 / -1

A body is projected up a smooth inclined plane with velocity v from the point A as shown in the figure. The angle of inclination is 45° and the top is connected to a well of diameter 40 m. If the body just manages to cross the well, what is the value of v? Length of the inclined plane is 20√2 m.

A
40 m s⁻¹

B
40√2 m s⁻¹

C
20 m s⁻¹

D
20√2 m s⁻¹

Solution
Question 9
4 / -1

The current i in a coil varies with time as shown in the figure. The variation of induced emf with time would be

A

B

C

D

Solution
Question 10
4 / -1

The radii of two planets are R₁ and R₂ and their densities are ρ₁ and ρ₂ respectively. If g₁ and g₂ represent the acceleration due to gravity at their respective surfaces, then g₁/g₂ is

A

B

C

D

Solution