Question

4.81e+20 electrons pass through a point in an electrical circuit every 4.96 seconds.
(a) 2080 C of charge pass through that point in how many minutes?
(b) The current though that point is ______ A.
(c) If the resistance of the circuit is 29.3 ? across this leg of the circuit, the voltage across this leg of the circuit is _______ V.

Answer 1

if 4.81e+20 electrons pass through a point in an electrical circuit every 4.96 seconds , the number of electrons passing throught the point per sec is 4.81*10^20/4.96= 96.975*10^18 electrons

from the definition of one C of charge is equal to 6.25*10^18 *fundamental charges

so 2080 C of charge = to 2080*6.25*10^18 fundamental charges

now time taken to 2080*6.25*10^18 fundamental charges pass through the point is

2080*6.25*10^18/96.975*10^18 = 134.05 s

which is equal to 2.234 min

(b) The current though that point is q= i*t

i= Q/t                     i= 96.9758*10^18/6.25*10^18                   ( each fundamental charge is equal to 1/6.25*10^18 C)

                               = 15.516 A

If the resistance of the circuit is 29.3 ohms across this leg of the circuit, the voltage across this leg of the circuit is

from Ohm's law V=i*R

                            = 15.516A*29.3 ohms =454.6188 V