Power and Electricity in the Home
- Created by: India.02
- Created on: 01-05-19 20:52
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- Power and Electricity in the Home
- Mains Supply
- The UK mains supply is an ac supply at around 230V
- In ac supplies, the current is constantly changing direction - produced by alternating potential difference in which the positive and negative ends keep alternating
- The frequency of the ac mains supply is 50 cycles per second or 50 Hz
- Cells and batteries supply direct current - dc
- Direct current is a current that is always flowing in the same direction - created by a direct potential difference
- Cables
- Appliances connected to mains supply by three-core cables - each with a copper core and a coloured plastic coating
- Neutral wire - blue - completes the circuit and carries the current away - electricity normally flows in through the live wire and out through the neutral wire - around 0V
- Live wire - brown - provides alternating potential difference (230V) from the mains supply
- Earth wire - green and yellow - stops appliance becoming live - doesn't usually carry current - only when there is a fault - around 0V
- The UK mains supply is an ac supply at around 230V
- Power
- Power of an appliance is the energy that it transfers per second
- Appliances often given a power rating - labelled with maximum safe power they can operate at - maximum operating power
- Tells you the maximum amount of energy transferred between stores per second when the appliance is in use
- Helps customers choose between models - lower power rating means that less electricity is used in a given time - cheaper to run
- Tells you the maximum amount of energy transferred between stores per second when the appliance is in use
- Higher power doesn't necessarily mean that it transfers more energy usefully - more powerful than another but less efficient - still only transfer the same amount of energy to the useful stores
- Appliances often given a power rating - labelled with maximum safe power they can operate at - maximum operating power
- Equations
- Transfer from Cells
- A moving charge transfers energy - charge does work against the resistance of the circuit
- No appliance transfers all energy completely usefully - higher the current, the more energy transferred to the thermal stores of the components
- Kettles transfer energy electrically from mains supply to thermal store in the heating element of the kettle
- Energy is transferred electrically from the battery of a handheld fan to the kinetic store of the fans motor
- No appliance transfers all energy completely usefully - higher the current, the more energy transferred to the thermal stores of the components
- A moving charge transfers energy - charge does work against the resistance of the circuit
- Power of an appliance is the energy that it transfers per second
- Energy Transferred
- When an electrical charge goes through a change in potential difference, energy is transferred
- A battery with a bigger p.d. will supply more energy to the circuit for every coulomb of charge which flows around it - the charge is raised up 'higher' at the start
- Energy is supplied to the charge at a power source to 'raise' it through a potential
- The charge gives up this energy when it 'falls' through any potential drop in components elsewhere in the circuit
- When an electrical charge goes through a change in potential difference, energy is transferred
- Mains Supply
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