Energy

Question 1

System

Answer 1

An object or group of objects.
When a system is in equilibrium, nothing changes so no energy is transferred.
When there is a change in a system, things happen so energy is transferred.

Question 2

Thermodynamic systems

Answer 2

A thermodynamic system can be isolated closed or open.

An open system allows the exchange of energy and matter to or from its surroundings.
A closed system can exchange energy but not matter to or from its surroundings.
An isolated system does not allow the transfer of matter or energy to or from its surroundings.

Question 3

Energy stores

Answer 3

Energy is stored in objects. When change occurs within a system, energy is transferred between objects or between stores.

Energy cannot be created or destroyed, it can only be transferred from one store to another. This means that for a closed system, the total amount of energy is constant.

Question 4

8 energy stores

Answer 4

Kinetic, gravitational, elastic, magnetic, electrostatic, chemical, nuclear, thermal.

Question 5

Energy transfer pathways

Answer 5

Energy is transferred between stores via transfer pathways.

Mechanical - when a force acts on an object.
Electrical - a charge moving through a potential difference.
Heating - energy is transferred from a hotter object to a colder one (conduction)
Radiation - energy transferred by electromagnetic waves.

Question 6

Kinetic energy

Answer 6

Ek = 1/2 mv^2

Ek = kinetic energy in joules (J)
M = mass in kg
V = velocity in m/s

Question 7

Gravitational potential energy

Answer 7

Eg = mgh

Eg = gravitational potential energy in joules (J)
M = mass in kg
G = gravitational field strength in N/kg
H = height in meters

Question 8

Elastic potential energy

Answer 8

Ee = 1/2 ke^2

Ee = elastic potential energy in joules (J)
K = spring constant N/m
E = extension in metres