Physics Test 295

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Physics Test 295

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Weekly Quiz Competition

Question 1
4 / -1

Two particles A and B of the same mass have their de-Broglie wavelengths in the ratio λ_A: λ_B= K : 1.

Their potential energies are in the ratio U_A: U_B= 1 : K².

The ratio of their total energies, E_A: E_B, is:

A
K²: 1

B
1 : K²

C
K : 1

D
1 : K

Solution
Question 2
4 / -1

An electron is accelerated under a potential difference of 64 V,

The de-Broglie wavelength associated with electron

A

B

C

D

Solution

Step 1: To find the de-Broglie wavelength associated with an electron accelerated under a potential difference of 64V, we use the de-Broglie wavelength formula:

where p is the momentum of the electron. The momentum p can be found using the kinetic energy gained by the electron due to the potential difference:
Question 3
4 / -1

A body of mass m is moved to a height equal to the radius of the earth R (above surface). The increase in its potential energy is:-

A
mgR

B
2 mgR

C
(1/2) mgR

D
(1/4) mgR

Solution
Question 4
4 / -1

A particle of mass m is located in a one dimensional potential field where potential energy is given by : V(x) = A(1 − cos⁡ px), Where A and p are constant.

The period of small oscillations of the particle is :-

A

B

C

D

Solution
Question 5
4 / -1

A uniform rod of mass m and length L is pivoted at its upper end and hangs vertically. A small block of mass m is placed on the horizontal floor directly below the pivot. The rod is released from rest when it makes an angle of 60^∘ with the vertical. If the coefficient of restitution for the collision between the lower end of the rod and the block is find the impulse imparted by the pivot on the rod during the collision. Assume the rod remains vertical after collision and the block does not rebound off the floor.

A

B

C

D

Solution
Question 6
4 / -1

Water from a hosepipe of radius 5cm strikes a wall at a speed of 5ms⁻¹ normally and stops.

The force exerted on the wall in newton is

A
13.5πN

B
6.25πN

C
62.5πN

D
27πN

Solution

To find the force exerted on the wall, we need to calculate the rate of change of momentum of the water striking the wall.
Question 7
4 / -1

An equilateral triangular loop with side length 1m carrying a current of 10A

μ₀= 4π × 10⁻⁷NA⁻²

The magnitude of the magnetic field at the center of the loop

A
18μT

B
1μT

C
9μT

D
3μT

Solution
Question 8
4 / -1

A coil of inductance 0.2H and 1.0Ω resistance is connected to a 90V source.

At what rate will the current in the coil grow at the instant the coil is connected to the source?

A
450 A s⁻¹

B
4.5 A s⁻¹

C
45 A s⁻¹

D
0.45 A s⁻¹

Solution

Step 1: At the instant the coil is connected (t = 0) the current is zero, so the voltage drop across the 1 Ω resistor is

V_R = iR = 0 V

Hence the entire 90 V of the source appears across the inductor:

V_L = 90 V

Step 2: The rate of change of current is governed by

Therefore the current grows at 450 A s⁻¹ the moment the coil is connected.
Question 9
4 / -1

An emf of 15V is applied in a circuit coil containing 5H inductance and 10Ω resistance.

The ratio of currents at time t = ∞ and t = 1s is

A

B

C
e⁻¹

D
none of these

Solution

Given: An emf of 15 V is applied in a circuit coil containing 5 H inductance and 10 Ω resistance.
Question 10
4 / -1

The resonant frequency of a series AC circuit consisting of a 200 μH inductor, a 0.0005 μF capacitor and a 10Ω resistance is

A
480kHz

B
503kHz

C
406kHz

D
607kHz

Solution

Key Concept

In a series LCR circuit, the resonant frequency is the frequency at which the inductive reactance equals the capacitive reactance, making the net reactance zero. At this frequency, the impedance is purely resistive and minimum.