GCSE Physics - P1 Energy

Energy stores

a system is an object or group of objects, when a system changes, the way energy is stored also changes

know changes of energy transfer e.g. bringing water to a boil in an electric kettle

examples of energy stores

vehicle slowing down, system is vehicle moving and when it slows down, the kinetic energy transfers to thermal due to friction between the wheels and brakes

how to calculate kinetic energy

E = ½ x mv²

E = joules

mass = kg

v = speed in m/s

How to calculate elastic potential energy

E = ½ x ke²

E = joules

k = spring constant in N/m

e = extension in m

How to calculate Gravitational Potential Energy

E = mgh

E = joules

m = mass in kg

g = gravitational field strength in N/kg (9.81)

h = height in meters

specific heat capacity definition

the amount of energy required to raise the temperature of 1kg of the substance by one degree celsius

How to calculate specific heat capacity

the energy required to raise the temperature of 1kg of a substance by 1 degrees or 1K

Energy = mass x specific heat capacity x temperature change

E = mcΔT
E = joules
m = mass in kg
c = specific heat capacity in J/(kg·K)
ΔT = change in temperature in K

How to calculate power

power = energy transferred/time = work done/time

P = E/t = W/t

power = watts (W)

energy = joules J

time = seconds

work done = joules J

1 joule per second = 1 watt

why can one motor do the same work but faster

energy is transferred at a faster rate

Energy transfers

energy can be transferred, stored or dissipated but cannot be created or destroyed. Energy is usually called wasted when dissipated

how to reduce energy waste

Lubrication:

• oil in a motor

• reduces friction

• so less energy is lost (as heat) through frction

Thermal insulation:

• double glazing

• less useful thermal energy is lost

thermal conductivity

The higher the thermal conductivity of a material, heat is allowed to travel through the material more easily, so the higher the rate of energy transfer by conduction across the material

thermal conductivity in a building

rate of cooling is low if walls are thickk and thermal conductivity walls are low. if the walls are thin metal sheets, heat would be lost very quickly

efficiency

ratio of useful work done by machine, engine, device to the energy supplied to it, which is often expressed as a percentage

efficiency = useful energy output/ total energy input = useful power output/total power input

how can efficiency be increased

• reducing waste output (lubrication, thermal insulation)

• reducing waste output (absorbing thermal waste and recycling as input energy)

non renewable energy sources

• fossil fuels (coal, oil, gas)

• nuclear fuel

renewable energy resources

• biofuel

• wind

• hydro-electricity

• geothermal

• tidal

• solar

• water waves

renewable and non-renewable energy

• renewable energy can be replenished (wind will never stop)

• non - renewable is used for large scale energy

• renewable resources cannot provide such a large amount of energy so easily

• renewable energy has become more important due to the finite lifetime of fossil fuels and so their development has become more important

• renewable energy is not always most reliable:

  solar doesnt work in bad weather

  wind is only intermittent

main energy uses

• transport

• electricity generation

• heating

environmental impact

• extraction of energy:

  fossil fuels involve destroying landscapes

  wind turbines can be considered an eyesore

• useful energy sources

  fossil fuels release harmful emissions

  solar, wind directly create electricity with no emissions

patterns an trends of energy use

During industrial revolution, fossil fuels became an important source of energy as it was easy to mine, and provided a lot of energy

- Only recently has renewable energy become more suitable

– technology has had to develop a lot since industrial revolution to be able to harness such energy sources efficiently

- It is easier to use energy resources due to increasing pressure to cope with the public’s increasing power demands but harder to solve environmental issues due to political, social, ethical and economic considerations.