CoachThe intensity of an electric current measures how strong the march is: how much electric charge parades past a point of the circuit each second — the current’s flow rate, as a river’s is water-per-second. Its unit is the ampere (), honoring a great pioneer of electricity’s laws; everyday circuits often speak in milliamperes: , a thousandth.
Examples
Example 55.2 (Amperes to know by sight)
A little indicator lamp sips about — ; a flashlight bulb, around ; the great lamp of a car’s headlight, ; a kettle at full roar, ; a starting car engine gulps from its battery; a lightning stroke, for its millisecond, rams tens of thousands of amperes down its channel. And the danger scale is sobering: currents of a few hundredths of an ampere across a human body can already be fatal — respect begins well below one ampere.
Example 55.7 (Reading the law’s fine print)
The law says along one loop, not whatever you do to the loop. Add a second lamp in series and the march weakens everywhere at once — perhaps drops to — but it weakens equally everywhere: the three tollbooths agree on the new number too. One loop, one intensity — whatever that intensity currently is.