12. Energy

Question 1

Energy stores

Answer 1

1. Kinetic store: moving object
2. Gravitational potential store: object at height
3. Elastic potential store: when objects are stretched or compressed
4. Chemical potential store: released through chemical reactions
5. Magnetic store: magnetic object in a magnetic field
6. Electrostatic store: object with charge in an electric field
7. Internal store: kinetic and potential energy of particles in an object
8. Nuclear store: released through nuclear reactions

Question 2

Internal Energy

Definition

Answer 2

The internal energy of a substance is the sum of kinetic energy due to the random motion of the particles and the potential energy due to forces of attraction between the particles.

Question 3

4 Ways Energy can be Transferred

Answer 3

Energy can be transferred:
1. Mechanically by a force acting over a distance
2. by heating due to a temperature difference
3. by propagation of waves
4. electrically by an electric current

Question 4

Principle of Conservation of Energy

Answer 4

The principle of conservation of energy states the energy can neither be created nor destroyed, but can be transferred from one body to another or converted from one form to another. The total energy in an isolated system is constant.

Question 5

Dissipation

Answer 5

If there is friction and air resistance, energy from the object/force will be dissipated to the surroundings as heat and sound.

Question 6

Power

Definition

Answer 6

Power is the rate of work done or the rate of energy transfer

P = E/t

Question 7

Efficiency

Calculation

Answer 7

useful energy output/total energy input x 100%
or
useful power output/total power input x 100%