Potential difference and power

Potential difference (p.d.) is a key concept in electricity. It measures how much energy is transferred to or from each coulomb of charge as it moves between two points in a circuit.

When a charge moves through a component (like a resistor or lamp), electrical energy is transferred. The potential difference across the component tells us how much energy is transferred per unit charge.

Formula for Potential Difference

The relationship between potential difference, energy, and charge is given by:

Where:

• $V$ = potential difference (volt, V)
• $W$ = energy transferred (joule, J)
• $Q$ = charge (coulomb, C)

Power in Electrical Circuits

Power is the rate at which energy is transferred or converted. In electrical circuits, power can be calculated using current and potential difference.

The basic formula for electrical power is:

Where:

• $P$ = power (watt, W)
• $V$ = potential difference (volt, V)
• $I$ = current (ampere, A)

Using Ohm’s law ($V = IR$), two other useful forms of the power equation are:

Where:

• $R$ = resistance (ohm, $\Omega$)

Example Calculations

Summary

• Potential difference is the energy transferred per coulomb of charge.
• Power in a circuit can be calculated using $P = VI$, $P = I^2 R$, or $P = \frac{V^2}{R}$.
• Remember to use the correct units: volts (V), coulombs (C), joules (J), amperes (A), ohms ($\Omega$), and watts (W).