Electric potential (voltage) describes potential energy per unit charge. This guide covers what it is, how to measure it, and why it matters.
What is Electric Potential?
Potential energy per unit charge at a point in an electric field. Measured in volts (V): 1 V = 1 joule per coulomb.
Key Concept
Voltage is like water pressure: charge flows from higher potential to lower potential.
Measuring Electric Potential
Common units:
- Volt (V) — SI unit
- Millivolt (mV) — 0.001 V
- Kilovolt (kV) — 1,000 V
- Megavolt (MV) — 1,000,000 V
Types of Voltage
Direct Current (DC) Voltage
- Batteries (AA 1.5V, 9V, 12V automotive)
- Solar panels
- DC power supplies
Alternating Current (AC) Voltage
- 120V/60Hz (North America)
- 230V/50Hz (Europe & most regions)
- 100V/50–60Hz (Japan)
How is Voltage Measured?
Use a voltmeter/digital multimeter:
- Set appropriate voltage range
- Connect in parallel with the circuit/component
- Read the display
Safety First!
Respect high voltage limits; verify meter range before measuring.
Common Voltage Levels
| Application | Voltage | Notes |
|---|---|---|
| AA/AAA Battery | 1.5V | Standard alkaline battery |
| USB Power | 5V | Standard USB power |
| Car Battery | 12V | Engine off nominal |
| Household (US) | 120V | North America standard |
| Household (EU) | 230V | Europe standard |
| High‑Voltage Transmission | 110kV–800kV | Long‑distance lines |
The Relationship: Voltage, Current, Resistance
V = I × R
For given resistance, higher voltage means higher current, and vice versa.
Practical Tip
Double‑check voltage requirements: too high damages parts; too low prevents operation.