Physics Test 209

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Physics Test 209

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Weekly Quiz Competition

Question 1
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If the binding energy of an electron in a hydrogen atom is 13.6 eV, then the energy required to remove the electron from the first excited state of Li⁺⁺ is

A
30.6 eV

B
13.6 eV

C
3.4 eV

D
122.4 eV

Solution

E₂ = -30.6 eV

Energy required to remove the electron from the first excited state of Li⁺⁺ = 30.6 eV
Question 2
4 / -1

Directions For Questions

Consider a block of conducting material of resistivity ρ shown in the figure. Current I enters the material at A and leaves from D. We apply the superposition principle to find the voltage ΔV developed between B and C. The calculation is done in the following steps.

(i) Take current I entering from A and assume it to spread over a hemispherical surface in the block.

(ii) Calculate field E(r) at a distance r from A by using Ohm's law, E = ρj, where j is the current per unit area at r.

(iii) From r dependence of E(r), obtain the potential V(r) at r.

(iv) Repeat (i), (ii) and (iii) for the current I, leaving D and superimpose results for A and D.

...view full instructions

For current entering at A, the electric field at a distance r from A is

A

B

C

D

Solution
Question 3
4 / -1

A parallel plate air-filled capacitor has a capacitance of 2 μF . When it is half-filled with a dielectric of dielectric constant k = 3, its capacitance becomes

A
4 μF

B
3 μF

C
1.5 μF

D
0.5 μF

Solution
Question 4
4 / -1

A coil having n turns and resistance RΩ is connected with a galvanometer of resistance 4RΩ. This combination is moved in time t seconds from a magnetic field W₁ weber to W₂ weber. The induced current in the circuit is

A

B

C

D

Solution
Question 5
4 / -1

Which of the following relations is/are correct?

A
Rolling friction > Sliding friction

B
Rolling friction < Sliding friction

C
Limiting friction < Sliding friction

D
Both (a) and (c)

Solution

Rolling friction is always less than the sliding friction because in sliding friction layer rubs each other due to which a lot of kinetic energy is converted heat energy.
Question 6
4 / -1

The ratio of the speed of sound in nitrogen gas to that in helium gas, at 300 K, is

A

B

C

D

Solution
Question 7
4 / -1

A cannon on a level plain is aimed at an angle α above the horizontal and a shell is fired with a muzzle velocity v₀ towards a vertical cliff, a distance R away. The height from the bottom at which the shell strikes the side walls of the cliff is

A

B

C

D

Solution

The time taken to move a horizontal distance R is Therefore, the vertical distance moved in this time is given by
Question 8
4 / -1

Directions: This question has Statement-I and Statement-II. Of the four choices given after the statements, choose the one that best describes the two statements.

Statement-I: Higher the range, greater is the resistance of ammeter.

Statement-II: To increase the range of ammeter, additional shunt needs to be used across it.

A
Statement-I is false, but Statement-II is true.

B
Statement-I is true and Statement-II is true. Statement-II is the correct explanation of Statement-I.

C
Statement-I is true and Statement-II is true. Statement-II is not the correct explanation of Statement-I.

D
Statement-I is true, but Statement-II is false.

Solution

For an ammeter, higher the range, lesser will be the value of the resistance of meter.

To increase the range of the ammeter, we have to add a resistance in parallel to the given device.

If R is the resistance of the given device, I_A is the maximum current which can be passed through it and R_s is the value of the shunt resistance.
Question 9
4 / -1

The two physical quantities among the following which don't have the same dimensions are

A
torque and work

B
momentum and Planck's constant

C
stress and Young's modulus

D
speed and (μ₀ɛ₀)^-1/2

Solution

E = hν, where h is Planck's constant.

h = E/ν

[h] = [M¹L²T^-2]/[T^-1] = [M¹L²T^-1]

Momentum = m × v

[p] = [M¹L¹T^-1]

Hence, Plank's constant and momentum have different dimensional formula.
Question 10
4 / -1

A particle falls from a height 'h' on a fixed horizontal plane and rebounds. If 'e' is the coefficient of restitution, the total distance travelled by the particle before it stops is

A

B

C

D

Solution