Electricity is measured in terms of amperage, voltage, and wattage.
- Amperage (amps for short) is a measure of the AMOUNT of electricity used.
- Voltage (volts) measures the pressure, or FORCE, of electricity.
- The amps multiplied by the volts gives you the wattage (watts), a measure of the WORK that electricity does per second.
Think of it this way: Electricity flowing through a wire is like water flowing through a garden hose. The amount of water that can fit through the hose depends on the diameter of the hose (amps). The pressure of the water depends on how far open the faucet is (volts). The amount of work that can be done (watts) depends on both the amount and the pressure of the water (volts x amps = watts).
All of the genuine Apple charging devices are dual voltage, which means that the internal circuitry does all the necessary transformations of the power to match what's coming out of the socket to what the device needs. This prevents too much power being sent to the device and causing any harm or damage. Most of Apple's devices also have circuitry to charge wattage.
