Watt's Law

Watt’s Law explains the relationship between power, voltage, and current in an electrical circuit. It helps determine how much electrical power is being used or produced.

Watt’s Law Formula:

P = V × I

• P = Power (in watts, W)
• V = Voltage (in volts, V)
• I = Current (in amperes, A)

Rearranged Forms:

• To find voltage: V = P / I
• To find current: I = P / V

Explanation:

Electrical power is the rate at which energy is consumed or generated. If you know any two of the three values (power, voltage, current), you can calculate the third using Watt’s Law.

Watt’s Law Practical Examples

Example 1: Finding Power (P)

A device runs on 240 V and draws 2 A of current. What is the power consumption?

Formula: P = V × I

Substitute the values: P = 240 V × 2 A = 480 W

Answer: The device uses 480 watts of power.

Example 2: Finding Voltage (V)

A device consumes 100 W of power and draws 5 A of current. What is the voltage?

Formula: V = P / I

Substitute the values: V = 100 W / 5 A = 20 V

Answer: The voltage is 20 volts.

Example 3: Finding Current (I)

A device uses 60 W of power and operates at 12 V. What is the current?

Formula: I = P / V

Substitute the values: I = 60 W / 12 V = 5 A

Answer: The current is 5 amperes.