Chapter 1: Energy

Power equation without pd(letters)

I(2)R

Power equation(letters)

V x A

Energy transferred equation(letters)

W x s

power of an appliance is the energy it

transfers per second

Total energy transferred depends on

how long the appliance is on its power

Live wire

can give you an electric shock

Earth wire

green and yellow, for safety and protects the wiring

Neutral wire

blue, completes the circuit and balances it

Live wire

brown, provides the alternating current

mains supply is

ac

battery supply is

dc

In cool conditions

the thermistor resistance goes up

In hot conditions

the thermistor resistance drops

In darkness

LDR resistance in at its highest

In bright light

LDR resistance falls

LDR is a resistor that is

dependent on the intensity of light

a thermistor is a

temperature resistor

ohmic conductors have a

constant resistance

resistance unit

ohm

Charge flow equation(letters)

Q=It

voltmeter measures

potential difference in volts

ammeter measures

current in amps

Pd equation

a x q

Electric current is the flow of

electrical charge

Doing work

Energy transferred. Done when current flows or by a force moving an object

Kinetic energy equation

1/2 x mass x speed

Gravitational Potential energy equation

Mass x gravitational strength x height

Elastic Potential energy equation

1/2 x spring constant x extension

Specific heat capacity

The amount of energy needed to raise the temperature ok 1kg of a substance by 1 Celsius

Specific heat capacity equation

Change in thermal energy = mass x specific heat capacity x temperature change

Conservation of energy principle

Energy can be transferred usefully, stored or dissipated but can never be created or destroyed

Power equations(2)

Power = Energy transferred / time or Power = work done / time

Power

Rate of doing work

Conduction

Is the process where vibrating particles transfer energy to neighbouring particles

Convection

Where energetic particles particles move away from hotter to cooler regions

Efficiency equations(2)

Efficiency = useful output energy transfer / total input energy transfer or efficiency = useful power output / total power input

Non-renewable

Will run out

Non-renewable energy resources

Coal, gas, oil

Renewable

Will never run out

Renewable energy resources

Solar, wind, water waves, hydro-electricity, bio-fuels, tides, geothermal

Bio-fuels

Energy created from plant products or animal dung

Hydro-electric power

Requires the flooding of a valley by building a big dam

Wave power

Turbines in the water

Solar cells

Generate electric currents directly from sunlight

Geothermal power

Possible in volcanic area or where hot rocks lie quite near

Wind power

Putting wind turbines in windy areas like Scotland