A potential difference of 12V is causing electrons to flow through a wire so that 20 x 1020 electrons pass a point in the wire in 1 minute.

i) What is the charge which passes the point in 1 minute, if the charge of each electron is 1.6 x 10-19C?
ii)What is the electric current in the wire?

Solution:
Number of electrons passes in = 1 minute= 60 seconds is n = 20 x 1020 through a wire at a point.

(i) Charge on one electron, e=1.6×10-19 C.
So, charge on n = 20 x 1020 electrons passing through the point in 1 minutes,
Q=ne   =20×1020×1.6×10-19   =320 C
(ii) Current in wire,
I=QtI=32060       =5.33 A

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