What an Ampere Is
Count the charge crossing a marked section of wire and divide by the time taken. The very same flow reads as 2 coulombs per second and as about 10¹⁹ electrons per second — one current described in two units that differ only by e. Switch the supply to AC and the running tally falls back to zero.
How to use this simulation
- Press Direct current and watch the coulomb count and the electron count climb together
- Press Alternating current to see the carriers reverse every half cycle
- Press Reset the count to start a fresh tally at the marked section
- Compare the two counters to confirm they differ by exactly the factor e
What to look for
- Two coulombs per second and 1.25 × 10¹⁹ electrons per second describe the same current
- Dividing the coulomb count by e always reproduces the electron count
- Under AC the tally climbs and falls, returning to zero after each complete cycle
- Carriers under AC never stop moving even though the net charge transferred is nil
- The ampere fixes only the rate of transfer, not what is doing the carrying
The physics behind it
The ampere is defined by I = Q/t: one ampere is one coulomb passing a section each second. Because charge is quantised, the same flow can be counted in carriers instead, N/t = I/e, which for one ampere is about 6.25 × 10¹⁸ electrons per second. The two descriptions differ only by the constant e. With alternating current the carriers reverse direction each half cycle, so the net charge transferred over a whole number of cycles is zero even though carriers are moving the entire time.