Physics Test 131

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Physics Test 131

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Question 1
4 / -1

Liquid cools from 50ºC to 45 ºC in 5 minutes and from 45ºC to 41.5ºC in the next 5 minutes. The temperature of the surrounding is :- [Assume newton's law of cooling is applicable]

A
27ºC

B
40.3ºC

C
23.3ºC

D
33.3ºC

Solution
Question 2
4 / -1

A long solenoid of self-inductance L and area of cross section A not carrying any current is placed in a uniform magnetic field of strength B with its axis parallel to the field direction. The total magnetic flux linked with the solenoid is φ. The energy of the magnetic field stored in the solenoid is

A

B

C

D
zero

Solution

Flux linked with each turn of the solenoid = BA
Total number of turns = nℓwhereℓ is the length of the solenoid
Question 3
4 / -1

All wires have same resistance and equivalent resistance between A and B is R. Now keys are closed, then the equivalent resistance will become:-

A
7R/3

B
7R/9

C
7R

D
R/3

Solution
Question 4
4 / -1

Steam at 100°C is passed into 1.4 kg of water kept in a calorimeter of water equivalent 0.03 kg at 20 °C till the temperature of the calorimeter and contents reach 80°C. Latent heat of steam is 2.26 × 10⁶ J kg ^{− 1} and sp.heat capacity of water is 4200 J /kg/°C. The mass of steam condensed in kilogram is nearly equal to

A
0.15 kg

B
0.16 kg

C
0.18 kg

D
0.20 kg

Solution

(M + M_w) C(80-20) = mL + mC(100 − 80)
(1.4 + 0.03) 4200 (80 − 20)= m × 2.26 × 10⁶ + m × 4200 × 20
1.43 × 4200 × 60= m (2.26 × 10⁶ + 4200 × 20)

= 0.1537 kg ≈ 0.15 kg
Question 5
4 / -1

A satellite orbiting around the earth of radius R is shifted to an orbit of radius 2R. The time taken for one revolution will increase nearly by

A
2 times

B
2.5 times

C
2.8 times

D
3.2 times

Solution

The time period of a satellite orbiting around the earth is
Question 6
4 / -1

Screw gauge shown in Figure has 50 divisions and in one complete rotation of circular scale the main scale moves 0.5 mm.

A
1.20 mm

B
2.46 mm

C
4.41 mm

D
4.46 mm

Solution

As shown in first figure the zero error of the screw gauge is:

ZE = 5×0.5 / 50 = 0.05mm

Least count of circular scale = 0.5 / 50 = 0.01mm

Circular scale reading = 25×0.01=0.25mm

Main scale reading = 2×0.5=1mm

Actual measurement is = MSR+CSR − ZE

1+0.25−0.05=1.20mm
Question 7
4 / -1

The given graph shows the extension (Δl) of a wire of length 1.0 m suspended from the top of a roof at one end and loaded at the other end. If the cross sectional area of the wire is 10^{− 6}m², the Young’s modulus Y of the material of the wire is

A
2 × 10^{− 7} Nm⁻²

B
3 × 10⁷ Nm⁻²

C
2 × 10¹¹ Nm⁻²

D
2 × 10⁹ Nm⁻²

Solution
Question 8
4 / -1

In Young’s double slit experiment, a monochromatic light of wavelength 5500 Å is used. The slits are 2 mm apart. The fringes are formed on a screen placed 20 cm away from the slits. It is found that the interference pattern shifts by 16 mm when a transparent plate of thickness 0.4 mm is introduced in the path of one of the slits. The refractive index of the transparent plate is

A
1.2

B
1.33

C
1.4

D
1.5

Solution
Question 9
4 / -1

The average degree of freedom per molecule of a gas is 6. The gas performs 25 J work, while expanding at constant pressure. The heat absorbed by the gas is:-

A
75 J

B
100 J

C
150 J

D
125 J

Solution

Change in the internal energy of gas is
Question 10
4 / -1

The radioactive sources A and B have half lives of 2hr and 4hr respectively, initially contain the same number of radioactive atoms. At the end of 2 hours, their rates of distintegration are in the ratio:-

A
4 : 1

B
2 : 1

C
√2 : 1

D
1 : 1

Solution

Given that the half-life of radioactive source A is, t_1/2 = 2 hr
half-life of radioactive source B is, t_1/2 = 4 hr
Decay constant of radioactive source A is,