Voltage Converter
Same value in every unit
| Unit | Value |
|---|
Reference points
- 1.5 V — an AA cell
- 3.7 V — a lithium-ion phone cell
- 5 V — USB
- 12 V — a car battery
- 230 V — mains in India, the UK and Europe
- 120 V — mains in the US, Canada and Japan
- 11 kV to 400 kV — distribution and transmission lines
Why transmission runs at hundreds of kilovolts
The power lost heating a cable is proportional to the square of the current. Carry the same power at a thousand times the voltage and you need a thousandth of the current, which cuts the loss by a factor of a million. That single relationship is why the grid looks the way it does, and why transformers sit between the line and your house.
The small end
Millivolts and microvolts are the language of measurement rather than power. A thermocouple gives tens of millivolts across a wide temperature range; an ECG trace is a few millivolts; radio signals arriving at an antenna are measured in microvolts. Everything after that is amplification.
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Frequently Asked Questions
230 V in India, the UK, Europe, Australia and most of Asia and Africa; 120 V in the United States, Canada and Japan. Both are nominal — the real supply varies by a few percent either side, and appliances are built to tolerate that.
Because power lost in a cable depends on the square of the current, not the voltage. Pushing the same power at 400,000 V instead of 400 V means a thousandth of the current and a millionth of the loss. The voltage is stepped back down near where it is used.
Signals rather than power. A thermocouple produces tens of millivolts, an ECG a few, and a microphone under one. The whole point of an amplifier is to lift these to something a circuit can work with.
CGS units from the older electromagnetic and electrostatic systems. They are here for reading old texts; nothing current is specified in them.
No.