Electrical appliances - extremely useful, transfer electrical energy to other forms of energy
Common electrical appliances: lamps, electrical mixers, speakers, tvs
Many electrical appliances transfer energy by heating - useful in things eg. kettles, but energy is often wasted - appliances designed to waste as little energy as possible
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P1.3.2 - Electrical Power
Power - rate at which appliance transfers energy
Watt (W) - 1W = 1J of electrical energy to other forms every second
Watt - too small - measured in kilowatts (kW) - 1kW = 1000W
P = E/t
P - power - W
E - energy - J
t - time for energy to be transferred - s
Efficiency = useful power in/total power in(X 100)
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P1.3.3 - Using Electrical Energy
Companies supplying mains electricity charge for amont energy used - measured in kilowatt-hour (kW h) - J is too small
Kilowatt-hour - amount of energy transferred by 1kW appliance when used for 1 hour
E = P x t E - energy transferred - kWh P - power of appliance - kW t - time taken for energy to be transferred - h
Electricity meter - records no of kWh of energy used - if previous meter reading is subtracted from current reading, electrical energy used between readings can be calculated
Total cost = no of kWh x cost/kWh
Cost/kWh is given on electricity bill
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P1.3.4 - Cost Effectiveness Matters
To compare cost effectiveness, must consider: - cost of buying appliance - cost of installing appliance - running costs - maintenance costs - environmental costs - interest charged on loan to buy appliance
To reduce energy bill - buy newer, more efficient appliances (eg. fridge), install materials designed to reduce energy waste (eg. loft insulation)
Payback time - time taken for appliance or installation to pay for itself in terms of energy savings
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