Chapter 8 : Generation of Electricity
Chapter 8.5
Cost of Electrical Energy Usage
Power, voltage and current rating of electrical appliances
Power is the energy used by an electrical appliance per second Power (W) =
Energy (J) Time (s)
Electric power is measured in units of Joule per second or watt (W) 1 000 W = 1 kW
Different electrical appliances has different power rating Electrical appliance
Voltage (V)
Power (W)
220 - 240
20
Electric home shower
240
3 300
Electric fan (type: 12 inch)
240
39
DVD video player
1
• Electrical energy used at home is measured by the electric meter. • The electrical energy usage is calculated using the following formula:
• Electrical energy usage is measured in kilowatthour (kwh).
• 1 kwh = 1 unit of electrical energy usage • The cost of electrical energy -used can be obtained using the following formula:
Example
Example
Extra
Extra
Chapter 8.5
Chapter 8 : Generation of Electricity
Cost of Electrical Energy Usage
Calculating the cost of electrical energy usage ď Ź
The electrical energy usage is measured in units of Joule (J) or kilowatt-hour (kWh)
Electrical energy (kWh) = Power (kW) x Time (h)
Sample of electric bill
2
Chapter 8 : Generation of Electricity
Q.R. 8.5
Quick Refresh
Power is the energy used by an electrical appliance per second Power (W) =
Energy (J) Time (s)
The relationship between power, voltage and current is show by the formula below
Power (P) = Voltage (V) x Current (I) The usage of electrical energy can be measured by applying the formula below
Electrical energy (kWh) = Power (kW) x Time (h)
3