# An ammeter measures a current of 3.2 amps. It does this in 2 minutes. a) calculate the charge flowing in this time b) how many electrons are flowing in those 2 minutes?

Asked on by kat10071

t-nez | High School Teacher | (Level 3) Associate Educator

Posted on

An ampere (amp) is a measure of current, which is flow of electrons in a circuit. It is equal to one Coulomb per second, with Coulomb (C) being a unit of  electrical charge. Knowing the amps and the time during which the current flowed you can find the total charge that went through the circuit.  Charge in Coulombs is converted to electrons using Faraday's constant which is 96,500 C, the charge on one mole of electrons. One mole of electrons = 6.02 x10^23.

Here's the calculation: (Notice that amps is replaced with Coulombs/sec)

2 minutes x 60 seconds/minute x 3.2 Coulombs/second = 384 Coulombs

384 Coulombs x 1 mole electrons/96,500 C  = 3.98 x 10^(-3) moles e-

3.98 x 10^(-3) moles e- x 6.02 x10^23 /mole = 2.40 x 10^21 electrons