Electric potential
Electric Fields - OCR A-Level Physics
Key Definition
Electric potential
The work done per unit positive charge in bringing a small test charge from infinity to that point. Measured in volts (V).
The work done per unit positive charge in bringing a small test charge from infinity to that point. Measured in volts (V).
$$V = \frac{Q}{4\pi\varepsilon_0 r}$$
$$V = \frac{Q}{4\pi\epsilon_0 r}$$
- Electric potentialThe work doneEnergy transferred when a force moves an object. In electrical circuits, W = QV (chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). times potential difference). per unit positive chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). in bringing a small test chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). from infinity to that point. is a scalarA quantity with magnitude only and no direction (e.g. mass, time, temperature). quantity - it has no direction. For multiple charges, add the potentials algebraically (with signs).
- A positive charge creates a positive potential that decreases with distance. A negative charge creates a negative potential that increases (becomes less negative) with distance.
- The potential differenceThe energyThe capacity to do work. Measured in joules (J). transferred per unit charge between two points. Measured in volts (V). between two points determines the work doneEnergy transferred when a force moves an object. In electrical circuits, W = QV (charge times potential difference).: W = $Q\Delta$V.
- EquipotentialsLines or surfaces of equal electric potential; no work is done moving a charge along an equipotential. are surfaces of constant potential. No work is done moving a charge along an equipotential.
- Equipotentials are always perpendicular to field lines.
Common Mistake
MEDIUM
Wrong: Treating electric potentialThe work doneEnergy transferred when a force moves an object. In electrical circuits, W = QV (charge times potential difference). per unit positive charge in bringing a small test charge from infinity to that point. as always positive.
Right: Potential around a negative charge is negative. When calculating the potential due to multiple charges, include the sign of each charge. The potential can be zero at a point between a positive and negative charge.
Right: Potential around a negative charge is negative. When calculating the potential due to multiple charges, include the sign of each charge. The potential can be zero at a point between a positive and negative charge.