Electric Charge, Current, Voltage, and Energy
The four essentials
Charge
Electric charge is a property of matter. In basic electronics, we usually think about electrons carrying negative charge and moving through conductors.
Current
Current is the amount of charge passing a point each second. The unit is the ampere, written as . One ampere means one coulomb of charge per second.
Voltage
Voltage is the electrical pressure that encourages charge to move. A battery creates a voltage difference between its terminals.
Energy and power
Electrical energy is what can do work, and power is the rate at which energy is used. Power is measured in watts, and a common relationship is .
Helpful analogy
You can think of voltage like water pressure, current like water flow, and resistance like a narrow pipe.
Units at a glance
| Quantity | Symbol | Unit |
|---|---|---|
| Charge | coulomb () | |
| Current | ampere () | |
| Voltage | volt () | |
| Power | watt () |
What is the unit of current?
Current is measured in amperes.
Correct answer: Ampere
Write the formula relating power, voltage, and current.
Power equals voltage times current.
Correct answer: P = VI
Voltage vs current
Voltage
- The push or potential difference
- Measured in volts
Current
- The flow of charge
- Measured in amperes