Which expression correctly defines electrical power in terms of voltage and current?

Which expression correctly defines electrical power in terms of voltage and current?

• A. P = I × R
• B. P = V ÷ I
• C. P = V × I
• D. P = V^2 × R

Answer: (C)

Power is the rate at which energy is transferred or used in a circuit. When you know the voltage across a device and the current flowing through it, you multiply them to get power: P = V × I. This works because voltage provides the energy per unit charge and current tells how many charges move each second, so their product is energy per second, i.e., watts. For example, if a device has 12 volts across it and draws 2 amperes, the power is 24 watts (12 × 2 = 24 W). Other forms don’t directly give power: P = I × R uses resistance and current (not power); P = V ÷ I gives resistance; P = V^2 × R isn’t a standard power expression (the correct related forms are P = VI, P = V^2 / R, or P = I^2R). The direct relationship using voltage and current is P = V × I.

Power is the rate at which energy is transferred or used in a circuit. When you know the voltage across a device and the current flowing through it, you multiply them to get power: P = V × I. This works because voltage provides the energy per unit charge and current tells how many charges move each second, so their product is energy per second, i.e., watts.

For example, if a device has 12 volts across it and draws 2 amperes, the power is 24 watts (12 × 2 = 24 W).

Other forms don’t directly give power: P = I × R uses resistance and current (not power); P = V ÷ I gives resistance; P = V^2 × R isn’t a standard power expression (the correct related forms are P = VI, P = V^2 / R, or P = I^2R). The direct relationship using voltage and current is P = V × I.