Edexcel A Level (IAL) Physics-2.33 Potential Difference- Study Notes- New Syllabus

Electric Potential Difference \( V = \dfrac{W}{Q} \)

The electric potential difference (voltage) between two points in a circuit tells us how much work is done per unit charge moved between those points. It is a measure of the energy transferred to or from each coulomb of charge.

Definition of Potential Difference

The potential difference between two points is defined as:

\( V = \dfrac{W}{Q} \)

• \( V \) = potential difference (volts, V)
• \( W \) = work done or energy transferred (joules, J)
• \( Q \) = charge moved (coulombs, C)

Interpretation:

• If \( V = 1\ \mathrm{V} \), then \( 1\ \mathrm{J} \) of energy is transferred per \( 1\ \mathrm{C} \) of charge.
• Higher voltage → more energy per coulomb.

Physical Meaning

• Voltage is “energy per charge”.
• A battery or power supply provides energy to charges.
• Charges lose energy when passing through resistors, lamps, motors, etc.
• Voltage across a component tells you how much energy each coulomb loses there.

Using \( V = \dfrac{W}{Q} \)

This formula is useful for:

• Finding energy transferred in a circuit
• Calculating charge moved through a component
• Relating electrical work to other forms of energy
• Understanding how batteries deliver energy

Rearranged forms:

\( W = VQ \)

\( Q = \dfrac{W}{V} \)

Energy Interpretation in Circuits

• A 9 V battery gives \( 9\ \mathrm{J} \) to every coulomb of charge.
• A lamp with \( 12\ \mathrm{V} \) across it takes \( 12\ \mathrm{J} \) of energy from every coulomb.
• Energy conservation applies: energy supplied by the source = energy used by components.