Electric Power

Key Notes:

Definition of Electric Power:

• Electric power is the rate at which electrical energy is consumed or produced by an electrical device.

• It is the amount of energy used per unit time.

Formula for Electric Power:

• The formula for electric power is:

P = VI

where:

P = Power (in watts)
V = Voltage (in volts)
I = Current (in amperes)

Another formula based on Ohm’s Law is:

P = I²R or P = V²R

SI Unit of Electric Power:

• The SI unit of electric power is the watt (W), where 1 watt equals 1 joule per second (1 W = 1 J/s).

Kilowatt and Megawatt:

• Large quantities of power are expressed in kilowatts (kW) and megawatts (MW).

1 kW = 1000 W, and 1 MW = 1,000,000 W.

Electrical Energy Consumption:

• Electrical energy consumed is calculated as:

Energy (in kWh) = Power (in kW) × Time (in hours)

• The unit of electrical energy consumed in households is kilowatt-hour (kWh), also known as a unit of electricity.

Applications of Electric Power:

• Electric power is used in various devices like household appliances, industrial machinery, and transportation systems.

• The amount of electric power used determines the electricity bill.

Efficiency of Electrical Devices:

• The efficiency of electrical devices is calculated using the ratio of useful power output to total power input, usually expressed as a percentage:

Efficiency = (Useful Power Output / Total Power Input)×100

Power Rating of Devices:

• Electrical devices have a power rating, indicating how much power they consume or deliver under standard operating conditions.
• For example, a 100 W light bulb consumes 100 watts of power when turned on.

Role in Circuits:

• In electrical circuits, the power dissipated by resistors, transferred by batteries, or consumed by other components is a crucial factor in designing and analyzing circuits.

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