Physics IGCSE - Energy, work and power

Different types of energy storage

Type of energy	Example
Chemical	fossil fuels
thermal	hot water
kinetic	moving objects
gravitational	roller coaster at the top
elastic	stretched elastic band
nuclear	nucleus of atom
electrostatic	two opposite charges held apart
electromagnetic	two opposite poles of 2 magnetic held apart

Describe how energy is transferred between stores during events and processes of transfer by forces (mechanical work done)

force is applied → moves an object through a distance

Describe how energy is transferred between stores during events and processes of electrical currents (electrical work done)

charges flow (electricity)

Describe how energy is transferred between stores during events and processes of heating and by electromagnetic

energy transferred between hot and cold

Describe how energy is transferred between stores during events and processes of sound and other waves

energy transferred as a wave (e.g. light wave)

Law of conservation of energy

energy cannot be created or destroyed, only transferred from 1 form

Apply this law of conservation of energy to simple examples including the interpretation of simple flow diagrams

Gravitational potential energy

- object gains GPE when lifted from ground

- object loses GPE when lowered towards ground

Gravitational potential energy (GPE) formula

GPE (J) = mass (kg) x gravitational acceleration (m/s²) x change in height (m)

E_p = mgΔh

Kinetic energy formula

Kinetic energy = ½ x mass x velocity²

E_k = ½ mv²

Work done = energy transferred

Work done

- product of force and distance moved in the direction of force

- measure of amount of energy transferred against resistive force

Work done formula

Work done (J) = force (N) x distance moved in direction of the force (m)

W = Fd = ΔE

Non - renewable

source cannot be replenished within human lifetime

Renewable

source easily replenished within human lifetime

Types of renewable and non - renewable energy

Non - renewable	Renewable
Nuclear fission	sun/solar
Fossil fuels	wind
	wave
	tidal
	hydroelectric
	geothermal
	biofuel

Examples of renewable and non - renewable energy

Energy	Examples
Nuclear fission	heat released from nuclear fission heats water → creates steam for turbine
Fossil fuels	generated in power plant → fuel is burned in boiler → steam to turn turbine
sun/solar	converts sunlight into electricity
wind	kinetic energy from win to turn blades → connected to rotor → drives generator
wave & tidal	convert kinetic energy of water → into mechanical energy → drives generator
hydroelectric	water flows through dams → spins turbine
geothermal	uses heat from earth’s core to create steam → steam spins turbine
biofuel	burned to heat water in boiler → steam that drives turbine to generator

Advantages and disadvantages of renewable and nonrenewable energy

	Advantages	Disadvantages
Renewable	- produces no pollutants	- high initial cost - weather dependent - takes up lot of space
Nonrenewable	- high energy output - cheap to run - reliable	- produces greenhouse gases and other pollutants - finite supply

Radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal

How the sun’s energy is released

by nuclear fusion in the sun

How is energy released

by nuclear fission in nuclear reactors

Energy efficiency

waste less energy as a proportion of input

Energy efficiency formula

Efficiency (%) = useful energy output/total energy input × 100%

Energy Efficiency formula (Power)

Efficiency (%) = useful power output/total power input x 100%

Power

work done per unit time/energy transferred per unit time

SIU: watts (W)

1W = 1J/s

Power Formula

power (W) = work done (J)/time (s) = energy transferred (J)/time (s)

P = W/t = ΔE/t

Power formula #2

Power (W) = force (N) x speed (m/s)

P = Fv

Describe how pressure varies with force and area in the context of everyday examples

the smaller the surface area is → the greater the pressure (e.g a nail of beds on your foot)

Pressure

force per unit area

SIU: pascal (Pa)

Pressure formula

pressure (Pa) = force (N)/area (m²)

p = F/A