Physics Test 170

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Physics Test 170

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Weekly Quiz Competition

Question 1
4 / -1

Heat is flowing through two cylindrical rods made of same materials whose ends are maintained at similar temperatures. If diameters of the rods are in ratio 1 : 2 and lengths in ratio 2 : 1, then the ratio of thermal current through them in steady state is :

A
1 : 8

B
1 : 4

C
1 : 6

D
4 : 1

Solution
Question 2
4 / -1

A balloon containing an ideal gas has a volume of 10 litre and temperature of 17ºC. If it is heated slowly to 75ºC, the work done by the gas inside the balloon is (neglect elasticity of the balloon and take atmospheric pressure as 105 Pa)

A
100 J

B
200 J

C
250 J

D
data insufficient

Solution
Question 3
4 / -1

In the P-V diagram shown. The gas does 5 J of work in isothermal process a b and 4 J in adiabatic process b c. What will be the change in internal energy of the gas in straight path c to a?

A
9 J

B
1 J

C
4 J

D
5 J

Solution

ΔU in a - b process = 0 (isothermal process)

in b - c process Q = 0 (adiabatic process)

∴ ΔU = - W = - 4 J

ΔU in cyclic process = 0

∴ ΔU in c - a process = 4J
Question 4
4 / -1

A monoatomic ideal gas is filled in a nonconducting container. The gas can be compressed by a movable nonconducting piston. The gas is compressed slowly to 12.5% of its initial volume. The percentage increase in the temperature of the gas is

A
400%

B
300%

C
– 87.5%

D
0%

Solution

Let initial temperature and volume be T₀ and V₀. Since the process is adiabatic, the final temperature and volume is (γ = 5/3 for monoatomic gas)

∴ percentage increase in temperature of gas is 4 x 100 - 100 = 300%
Question 5
4 / -1

A diatomic ideal gas is heated at constant volume until the pressure is doubled and again heated at constant pressure until volume is doubled. The average molar heat capacity for whole process is:

A
13R/6

B
19R/6

C
23R/6

D
17R/6

Solution

Let initial pressure, volume, temperature be P₀, V₀, To indicated by state A in P-V diagram. The gas is then isochorically taken to state B (2P₀, V₀, 2T₀) and then taken from state B to state C (2P₀, 2V₀, 4T₀) isobarically.
Question 6
4 / -1

The ratio of final root mean square velocity to initial root mean square velocity of nitrogen molecules if nitrogen gas is compressed adiabatically from a pressure of one atmosphere to a pressure of two atmosphere is :

A
2^2/7

B
2^1/7

C
2^1/5

D
2^2/5

Solution
Question 7
4 / -1

Four particles have velocities 1, 0, 2, 3 m/s. The root mean square velocity of the particles is: (in m/s)

A
3.5

B

C
1.5

D

Solution
Question 8
4 / -1

V–T diagram for a process of a given mass of ideal gas is as shown in the figure. During the process pressure of gas.

A
first increases then decreases

B
continuously decreases

C
continuously increases

D
first decreases then increases

Solution
Question 9
4 / -1

A slab X of thickness ‘t’, thermal conductivity ‘K’ and area of cross-section ‘A’ is placed in thermal contact with another slab Y which is 2n² times thicker, 4n times conductive and having n times larger cross section area. If the outside face of X is maintained at 100°C, the outside face of Y at 0°C, then the temperature of the junction θ is represented by the graph (n > 0) :

A

B

C

D

Solution
Question 10
4 / -1

Two conducting movable smooth pistons are kept inside a non conducting, adiabatic container with initial positions as shown. Gas is present in the three parts A, B & C having initial pressures as shown. Now the pistons are released. Then the final equilibrium position length of part A will be

A
L/8

B
L/4

C
L/6

D
L/5

Solution