Power in Appliances
Many appliances have different power rating
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An electricity meter is used to measure the amount of energy consumed by a household. |
The kilowatt-hour (kWh) is a unit of ENERGY (NOT power) and is calculated by
Energy transferred = Power x Time
(kWh) (kW) (hours, h)
Energy transferred = Power x Time
(kWh) (kW) (hours, h)
EXAMPLE
A 2000W electric fire is used for 10 hours.
What is the cost, at 8¢ per kWh?
Solution
Energy transferred = Power x Time
(kWh) (kW) (hours, h)
E = 2 kW x 10 hours
E = 20 kWh
Cost at 8¢ per kWh = 20 kWh x 8 ¢ = $1.60
A 2000W electric fire is used for 10 hours.
What is the cost, at 8¢ per kWh?
Solution
Energy transferred = Power x Time
(kWh) (kW) (hours, h)
E = 2 kW x 10 hours
E = 20 kWh
Cost at 8¢ per kWh = 20 kWh x 8 ¢ = $1.60
Fuses
Circuit Breakers
Fuses and circuit breakers are always placed in the live wire.
What is the main difference between a circuit breaker and fuse?
The main difference between a circuit breaker and fuse is that the circuit breaker can be reset (eg. manually) whereas a fuse would need to be replaced, since it is destroyed when excess current flows through it.
HOUSEHOLD WIRING
The current supplied to a home is an alternating current.
In a fused plug there are three wires
1.Live – brown wire.
2.Neutral – blue wire.
3.Earth – green & yellow wire.
In a fused plug there are three wires
1.Live – brown wire.
2.Neutral – blue wire.
3.Earth – green & yellow wire.
EXAMPLE
A vacuum cleaner has a rating of 460W on the 230V mains. What fuse should be fitted in the plug?
Solution
P = I x V
I = P/V
I = 460/230
I = 2A
A 3A fuse should be fitted.
A 13A fuse could allow a damaging current to flow before melting.