Electromotive force and potential difference are mentioned when speaking about voltages in a circuit.
Challenge
1) Electromotive force is associated with devices that add power to the circuit (a.k.a. active devices).
- False
- True
Electromotive force
Electromotive forces cause the potential difference in the circuit. The electric potential at one terminal is made to be greater compared to the other terminal.
EMF is responsible for taking the charge up the proverbial hill.
Potential difference
This is the drop in electric potential between two points. When two points are connected via a conductor and there is a potential difference between the two points, a current flows between the two points in order to balance the potentials between the two points. If there is no PD, there is no current.
PD is when the charge rolls down the hill.
Differences between EMF and PD
| Aspect | EMF | PD |
|---|---|---|
| Definition | Max voltage available from a power source | Voltage drop across a device |
| Associated devices | Active devices | Passive devices |
| Examples of devices | Batteries, generators | Resistors, motors, heating elements |
| Effect of resistance | Not affected by resistance | Changes with resistance |
| Energy in circuit | Energy is gained | Energy is lost |
| Change in electric potential | Increases potential | Decreases potential |
| Current | Present regardless of current | No current, no PD |