Why Power Matters in Electrical Circuits

⚙️ Why Power Matters in Electrical Circuits

For electrical devices, power can also be calculated using voltage and current. This is important because electricity bills are based on the energy used — and energy used depends on both power and time.

P = I × V   Power (W) = Current (A) × Voltage (V)

Rearranging gives us more useful forms:

• P = I²R — useful when you know current and resistance
• P = V²/R — useful when you know voltage and resistance

In domestic settings, energy companies charge by the kilowatt-hour (kWh):

Energy (kWh) = Power (kW) × Time (h)

For example, a 3 kW kettle running for 0.05 hours (3 minutes) uses: 3 × 0.05 = 0.15 kWh of electrical energy.