# Physics - energy

• Created by: midget17
• Created on: 31-03-18 14:57
Types of energy
Electrical, light, kinetic, gravitational potential, thermal, chemical, elastic potential, sound
1 of 22
How can energy be transferred?
Heating, waves or by a force when it moves an object
2 of 22
Closed system
A system in which no energy transferes take place out of or into the enery stores of the system
3 of 22
Conservation of energy
Energy can't be created or destroyed.
4 of 22
Work done equation
force (N) x distance moved along line of force (m) = work done (J)
5 of 22
Gravitational potential energy increases when...
...it moves up and decreases when it moves down
6 of 22
Change in GPE equation - using weight
weight (N) x change in height (m) = change in GPE (J)
7 of 22
Chnage in GPE equation - using mass
mass (kg) x gravitational field strength (N/kg) x change in height (m) = change in GPE (J)
8 of 22
Kinetic energy equation
Kinetic energy (J) = 1/2 x mass (kg) x speed2^ (m/s)
9 of 22
Elastic potential energy equation
Elastic potential energy (J) = 1/2 x spring constant (N/m) x extension2^ (m)
10 of 22
What happens to waste energy in any system?
It is dissipated (spreads out) and may be stored in less useful ways.
11 of 22
Efficiency of a device
useful output energy / total output energy (J)
12 of 22
How do machines waste energy?
Friction between moving parts causes heating, resistance of wire causes it to get hot when current passes through it, air resistance and sound
13 of 22
Improving efficiency of devices
Lubricate moving parts to reduce friction, (in circuits) use wires with little electrical resistance, streamline shapes of moving objects to reduce air resistance, cut out noise (e.g. tighten object to reduce vibration)
14 of 22
Light bulb - useful energy and waste energy
Useful - light, waste - heat from filament
15 of 22
Electric heater - useful energy and waste energy
Useful - thermal energy, waste - light emitted from glowing element
16 of 22
Electric toaster - useful energy and waste energy
Useful - energy heating bread, waste - energy heating toaster case
17 of 22
Electric kettle - useful energy and waste energy
Useful - heating water, waste - heating kettle itself
18 of 22
Hairdryer - useful energy and waste energy
Useful - kinetic energy of air driven by fan, energy heating air flowing past filament, waste - sound of fan motor, energy heating hairdryer itself
19 of 22
Electric motor - useful energy and waste energy
Useful - kinetic energy of object driven by motor, GPE of object lifted by motor, waste - energy heating motor, sound waves generated by motor
20 of 22
Power equation
enery transferred (J) / time taken (sec) = power (W)
21 of 22
Power wasted by an appliance =
Total power input - useful power output
22 of 22

## Other cards in this set

### Card 2

#### Front

How can energy be transferred?

#### Back

Heating, waves or by a force when it moves an object

Closed system

### Card 4

#### Front

Conservation of energy

### Card 5

#### Front

Work done equation

## Similar Chemistry resources:

See all Chemistry resources »See all Atoms and compounds resources »