2: Heat Capacity

Question 1

What is heat? What is its unit?

Answer 1

Heat is the energy transferred from one body to another as a result of a temperature difference. Its unit is joule(J).

Question 2

What is another way to increase the internal energy of a body?

Answer 2

Doing work

Question 3

What is power and what is its unit and formula?

Answer 3

Power measures the rate of energy transfer in watt. It equals the energy transferred divided by the time (P=E/t)

Question 4

1W=?J

Answer 4

1Js^-1 (joule per second)

Question 5

What is the conversion between watt, kilowatt, and megawatt?

Answer 5

1MW=1000kW=1,000,000w
1kW=1000W

Question 6

What is a common unit for energy in terms of watt and what is its relationship with Joule?

Answer 6

kW h (kilowatt-hour)
1kW h=3,600,000J=3.6 x 10⁶J=3600kJ

Question 7

What can be used to measure the electrical energy supplied to an electrical device?

Answer 7

joulemeter (for low-voltage power supplies) or Kilowatt-hour meter (for mains)

Question 8

What is heat capacity and what is its unit?

Answer 8

Heat capacity measures the amount of energy to heat up a body by 1°C. It is measured in J °C^-1 (joule per degree celcius) or J K^-1 (joule per kelvin).

Question 9

What is the formula for heat capacity?

Answer 9

Heat capacity = energy divided by the change in temperature (C=E/dT, E = C x dT)

Question 10

What is specific heat capacity and what is its unit?

Answer 10

Specific heat capacity measures the amount of energy to heat up 1kg of a substance by 1°C. It is measured in J kg^-1°C^-1.

Question 11

What is the formula for specific heat capacity?

Answer 11

Specific heat capacity=Heat capacity divided by unit mass (c=C/m) and the power divided by the change in temperature and the mass (c = E/dT x m, E = m x c x dT)

Question 12

What is the law of conservation of energy and what can be inferred from it about heat transfer, assuming that there is no loss of energy to the surroundings?

Answer 12

Energy cannot be created or destroyed. The total amount of energy in a closed system is conserved. Therefore, in the process of heat transfer, the energy lost by the hotter body is equal to the energy gain by the colder body.

Question 13

List 3 usages of water making use of its high specific heat capacity.

Answer 13

1. Water coolant: water is used to cool motor cars, power stations, and spacesuits/cooling vests
2. regulating body temperature: 60%-70% of our bodies is made up of water, helping our body temperture tog stay constant when the temperture of the surroundings change.
3. Climatic effect: coastal areas have milder seasons compared to inland areas.