Electric current is the flow of electric charge. This guide covers definition, units, types, conversion, measurement, circuits, applications, safety, and everyday examples.
What is Electric Current?
Rate of charge flow past a point. Symbol I. Measured in amperes (A).
Key Formula:
I = Q / t (I amps, Q coulombs, t seconds).
Units of Electric Current
Ampere (A)
SI base unit; 1 A = 1 C/s
1 A = 1 C/s
Milliampere (mA)
1/1000 of an ampere
1 mA = 0.001 A
Microampere (μA)
1/1,000,000 of an ampere
1 μA = 0.000001 A
Types of Electric Current
Direct Current (DC)
Flows in one direction.
- Constant polarity
- From batteries/solar
- Used in electronics
- Examples: phones, EVs
Alternating Current (AC)
Reverses direction.
- Has frequency
- From generators
- Power distribution
- Examples: mains, lines
Current Conversion Table
| Unit | Amperes (A) | Milliamperes (mA) | Microamperes (μA) | Kiloamperes (kA) |
|---|---|---|---|---|
| 1 A | 1 | 1,000 | 1,000,000 | 0.001 |
| 1 mA | 0.001 | 1 | 1,000 | 0.000001 |
| 1 μA | 0.000001 | 0.001 | 1 | 0.000000001 |
| 1 kA | 1,000 | 1,000,000 | 1,000,000,000 | 1 |
Did You Know?
The ampere was redefined in 2019 using the fixed value of the elementary charge e.
Measuring Electric Current
Ammeters
Series connection to measure I.
Multimeters
Measure I/V/R; choose proper range.
Clamp Meters
Sense magnetic field without opening circuit.
Current in Electrical Circuits
Conventional current flows + to −; electrons opposite. Related to V and R (Ohm’s Law).
Ohm's Law:
V = I × R
Current in Series and Parallel Circuits
Series Circuits
- I same through components
- R total sums
- V divides
- Example: series lights
Parallel Circuits
- V same on branches
- I splits
- R total smaller
- Example: household wiring
Applications of Electric Current
Electronics
- Computers/phones
- Audio/video
- MCUs/embedded
Power Systems
- Generation
- Transmission/distribution
- Motors/generators
Medical
- ECG
- Defibrillators
- TMS
Industry
- Electroplating
- Welding
- Electromagnets
Safety Warning:
As little as ~100 mA through the heart can be fatal. De‑energize and follow safety rules.
Current in Everyday Life
Household Appliances
- LED: 0.02–0.83 A
- Fridge: 0.5–2 A
- Microwave: 5–10 A
- Hair dryer: 8–15 A
Electronics
- Phone charge: 1–2 A
- Laptop charge: 1.5–3 A
- USB: 0.5–3 A
Industrial
- EV charger: 12–80 A
- Industrial motor: tens–hundreds A
- Lightning: 10k–200k A
Practical Tip:
Measure current in series; start at highest range. Use AC range for AC.