domestic uses amd energy transfers

Power transfers

Power transfer is the rate at which energy is transferred and is directly proportional to the product of the potential difference across a device and the current through it

Explain the relationship between power and voltage or current

This means if either voltage or current increases, the power (and thus the rate of energy transfer) increases.

Power explanation

As electrons flow through wires, they collide with the ions in the wire which causes the ions to vibrate more. This increased vibration of the ions increases the temperature of the wire. Energy has been transferred from the chemical energy store of the battery into the internal energy store of the wire

Energy transfers depend on

how long the appliance is switched on for and the power of the appliance

domestic electricity supply (Uk)

Frequency of 50Hz and about 230V

Alternating current

Constantly changing direction, positive and negative voltages indicating direction of flow. Used in uk mains

Direct current

Only flows in one direction

Examples of direct current uses

Car batteries

Dry cells

Solar cells

Reasons for being AC used in uk mains

Less of a fire risk- sudden discharge of electricity is less severe

Easy voltage conversions- easier to increase or decrease using transformers, so safer and more efficient

Cost effective- easier and cheaper to generate at high power levels as concert kinetic energy into electrical energy

Live wire

(Brown) brings alternating current from the supply

Neutral wire

(Blue) completes the circuit

Earth wire

(Green and yellow stripes) as safety to stop appliance “going live”, should not carry charge unless faulty

Dangers of live wires

They carry charge and so can electrocute you if you touch it. Even if the circuit is open, it can still carry charge.

Live wire and earth wire touching?

Can create a dangerously short circuit, potentially causing fires or electrocution

When is work done

When charge flows through a circuit

Relationship between power rating and stored energy

higher power rating signifies a faster change in stored energy