Physics Test 123

Result

Physics Test 123

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Question 1
4 / -1

A α−particle passes through a potential difference of 2×10⁶V and then it becomes incident on a silver foil. The charge number of silver is 47. The energy of incident particles will be: (in joule)

A
5×10⁻¹²

B
6.4×10⁻¹³

C
5.8×10⁻¹⁴

D
9.1×10⁻¹⁵

Solution

Energy of incident particles ie, alpha particles will be
Question 2
4 / -1

A pipe of length 85 cm is closed from one end. Find the number of possible natural oscillations of air column in the pipe whose frequencies lie below 1250 Hz. The velocity of sound in air is 340 m/s.

A
12

B
8

C
6

D
4

Solution
Question 3
4 / -1

Three identical spheres, each of mass 1 kg are kept as shown in the figure below, touching each other, with their centres on a straight line. If their centres are marked P, Q, R respectively, the distance of centre of mass of the system from P is

A

B

C

D

Solution

Radius

r₁= 0

r₂ = PQ

r₃ = PR

the distance of centre of mass of the system from 'P' is given by
Question 4
4 / -1

A resistor R and 2μF capacitor in series is connected through a switch to 200 V direct supply. Across the capacitor is a neon bulb that lights up at 120 V. Calculate the value of R to make the bulb light up 5 s after the switch has been closed (log₁₀ 2.5 = 0.4)

A
1.7 × 10⁵ Ω

B
2.7 × 10⁶Ω

C
3.3 × 10⁷ Ω

D
1.3 × 10⁴Ω

Solution

Wen Neon bulb is fulled with gas.

No, current frows through it because the resistance is infine.
Question 5
4 / -1

Direction: Question is based on the following paragraph.

A wire of length L, mass m and carrying a current is suspended from point O as shown. An infinitely long wire carrying the same current I is at a distance L below the lower end of the wire. Given, I = 2A, L= 1m and m = 0.1 kg (ln 2 = 0.693)

What is angular acceleration of the wire just after it is released from the position shown?

A

B

C

D

Solution
Question 6
4 / -1

The figure shows three circuits with identical batteries, inductors and resistances. Rank the circuits according to the currents through the battery just after the switch is closed, greatest first

A
i₂ > i₃> i₁

B
i₂ > i₁ > i₃

C
i₁ > i₂> i₃

D
i₁ > i₃ > i₂

Solution

In circuit ( 1 ), on closing the switch, the current in the inductor is zero due to self induction, ie, i₁=0.

In circuit (2), on closing the switch the current in the inductor is zero due to self-induction.

Therefore,

i₂= i′ = E / R1
In circuit (3), on closing the switch, the current in the inductor is again zero due to the same reason.

Therefore,

i₂= i′ = E / (R1 + R2)

Thus, it is obvious that,

i2>i3>i1(=0)
Question 7
4 / -1

A bullet when fired into a fixed target loses half of its velocity after penetrating 20 cm.How much further it will penetrate before coming to rest?

A
6.66 cm

B
3.33 cm

C
12.5 cm

D
10 cm

Solution
Question 8
4 / -1

Directions: Question are Assertion - Reaction type each of these contains two statements: Statement I (Assertion), Statement II (Reason) Each of these questions also has four alternative choices, only one of which is correct. You have to select the correct choices from the codes a, b, c and d given below:

Statement I : The isothermal curves intersect each other at a certain point

Statement II: The isothermal changes takes place slowly, so the isothermal curves have very little slope.

A
Statement I is true; Statement II is true; Statement II is not a correct explanation for Statement I.

B
Statement I is true; Statement II is false.

C
Statement I is false; Statement II is true.

D
Statement I is true; Statement II is true; Statement I is not a correct explanation for Statement II.

Solution

To carry out isothermal process, a perfect gas is compressed or allowed to expand very slowly. Isothermal curves never intersect each other as they have very little slope.
Question 9
4 / -1

A parallel plate air capacitor has a capacitance C. When it is half filled with a dielectric of dielectric constant 5, the percentage increase in the capacitance will be

A
400 %

B
66.6%

C
33.3%

D
200%

Solution
Question 10
4 / -1

A ball is dropped from a bridge at a height of 176.4 m over a river. After 2s, a second ball is thrown straight downwards. What should be the initial velocity of the second ball so that both hit the water simultaneously? (Take g=10m/s²)

A
2.45 ms^-1

B
49 ms^-1

C
25.7 ms^-1

D
24.5 ms^-1

Solution