The first law of thermodynamics can be written as an equation, Q = ΔU + W.
A sealed cylinder contains helium gas.
The cylinder containing the helium gas is heated.
The cylinder has fixed dimensions.
(i) Which quantity increases for the helium atoms, when the cylinder is heated?
(1)
A average density of the atoms
B average kinetic energy of the atoms
C total number of atoms
D volume of each atom
(ii) The gas cylinder contains helium gas at a temperature of 283 K.
The pressure of the gas is 3.0 × 105 Pa.
The volume of the gas remains constant at 0.1 m3.
The temperature of the helium gas increases to 333 K.
Calculate the new pressure of the gas at 333 K.
(3)
Use the equation:
Show your working.
pressure = ........................................................... Pa
(Total for question = 4 marks)
Q2.
(i) A boiler gives out 3.5 × 109 J of energy to heat a home each year.
To produce this amount of energy, the boiler takes in 2.9 × 1010 J.
, (2)
Calculate the efficiency of the boiler.
Use the equation:
Show your working.
efficiency of boiler = ...........................................................
(ii) Give a value for an amount of energy that the boiler should take in to increase its efficiency.
(1)
.............................................................................................................................................
(Total for question = 3 marks)
Q3.
Steel bolts are used to hold the engine of a car in place.
One of the steel bolts is stress tested.
(i) The length of the bolt is 10.0 cm before testing.
During the test when the work done on the bolt is 100 J, its length is 10.4 cm.
Calculate the force applied to the bolt when its length is 10.4 cm.
Use the equation
work done in stretching = 1⁄2 F Δx
Show your working.
(4)
, force applied = ........................................................... N
(ii) Figure 3 shows the data from the stress test of the steel bolt.
Figure 3
Explain the behaviour of the steel between points:
- O to A
- B to C.
(6)
(Total for question = 10 marks)
Q4.
A refrigerator is a type of heat pump.
The contents of a refrigerator are kept at a temperature of 6°C.
The thermal energy taken out of the refrigerator is 4 680 000 J.
The refrigerator has an efficiency of 0.35.
Calculate the input energy to the refrigerator.
(4)
Use the equation:
Show your working.
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