Heat and Thermodynamics - SS1 Physics Past Questions and Answers - page 2
Which of the following is an example of the practical application of thermal expansion?
Expansion joints in bridges and buildings.
Measuring the temperature of an object using a thermometer.
Generating electricity from solar panels.
Allowing liquids to freeze and expand in containers.
A steel rod measures 2 metres at 20°C. If the coefficient of linear expansion for steel is 12 x 10-6 /°C, what will be the length of the rod when the temperature rises to 50°C?
Change in length = (coefficient of linear expansion) x (original length) x (change in temperature)
Change in length = (12 x 10-6 /°C) x (2 metres) x (50°C - 20°C)
Change in length = 12 x 10-6 x 2 x 30
Change in length = 7.2 x 10-4 metres
Length of the rod at 50°C = original length + change in length
Length of the rod at 50°C = 2 metres + 7.2 x 10-4 metres
Length of the rod at 50°C = 2.00072 metres
A copper pipe has an original length of 5 metres at 25°C. If the coefficient of linear expansion for copper is 16 x 10-6 /°C, what temperature change is required for the pipe to increase its length by 1 centimetre?
Change in length = (coefficient of linear expansion) x (original length) x (change in temperature)
Change in length = (16 x 10-6 /°C) x (5 metres) x (change in temperature)
Change in length = 0.00008 x (change in temperature)
Given that the change in length is 1 centimetre = 0.01 metres, we can solve for the change in temperature:
0.00008 x (change in temperature) = 0.01 metres
(change in temperature) = 0.01 metres / 0.00008
(change in temperature) = 125°C
Therefore, a temperature change of 125°C is required for the copper pipe to increase its length by 1 centimetre.
A glass jar has an internal volume of 500 cm³ at 25°C. If the coefficient of volume expansion for glass is 30 x 10^-6 /°C, what will be the volume of the jar when the temperature rises to 50°C?
Change in volume = (coefficient of volume expansion) x (original volume) x (change in temperature)
Change in volume = (30 x 10^-6 /°C) x (500 cm³) x (50°C - 25°C)
Change in volume = 30 x 10^-6 x 500 x 25
Change in volume = 0.375 cm³
Volume of the jar at 50°C = original volume + change in volume
Volume of the jar at 50°C = 500 cm³ + 0.375 cm³
Volume of the jar at 50°C = 500.375 cm³
Heat transfer by direct contact or collision of molecules is known as:
Conduction
Convection
Radiation
None of the above
Heat transfer through the movement of fluids (liquids or gases) is called:
Conduction
Convection
Radiation
None of the above
Which of the following is an example of heat transfer by radiation?
Holding a hot cup of coffee
Cooking food in a boiling pot
Feeling the warmth of the sun on your skin
None of the above
Heat transfer by electromagnetic waves is known as:
Conduction
Convection
Radiation
None of the above
Which type of heat transfer does not require a medium or direct contact?
Conduction
Convection
Radiation
None of the above
Insulation in buildings is primarily used to reduce which type of heat transfer?
Conduction
Convection
Radiation
None of the above