Electric Potential
- In order to move a positive charge closer to another positive charge, work must be done to overcome the force of repulsion between them
- Similarly, to move a positive charge away from a negative charge, work must be done to overcome the force of attraction between them
- Energy is therefore transferred to the charge that is being pushed upon
- This means its potential energy increases
- If the positive charge is free to move, it will start to move away from the repelling charge
- As a result, its potential energy decreases back to 0
- This is analogous to the gravitational potential energy of a mass increasing as it is being lifted upwards and decreasing as it falls
- The electric potential at a point is defined as:
The work done per unit positive charge in bringing a point test charge from infinity to a defined point
- Electric potential is a scalar quantity
- This means it doesn’t have a direction
- Even though electric potential is a scalar quantity, it can take a positive or negative sign, this is because the electric potential is:
- Positive around an isolated positive charge
- Negative around an isolated negative charge
- Zero at infinity
- Positive work is done by the mass from infinity to a point around a positive charge and negative work is done around a negative charge. This means:
- When a positive test charge moves closer to a negative charge, its electric potential decreases
- When a positive test charge moves closer to a positive charge, its electric potential increases
- To find the potential at a point caused by multiple charges, the total potential is the sum of the potential from each charge
The electric potential V decreases in the direction the test charge would naturally move in due to repulsion or attraction
