A) 144 C
The electric current is defined as
[tex]I=\frac{q}{t}[/tex]
where
q is the charge passing a given point of the circuit in a given time
t is the time interval considered
For this bulb, we know that:
I = 0.20 A is the current
[tex]t=12 min \cdot 60 = 720 s[/tex] is the time considered
Therefore, the amount of charge passing the point in the circuit in this time is
[tex]q=It = (0.20)(720)=144 C[/tex]
B) [tex]9\cdot 10^{20}[/tex] electrons
The charge of one electron is
[tex]e=1.6\cdot 10^{-19}C[/tex]
And the total charge passing through the point in the circuit in 12 min is
[tex]q=144 C[/tex]
So the total charge can be written as
[tex]q=ne[/tex]
where
n is the number of electrons passing that point of the circuit in 12 min
So, solving for n,
[tex]n=\frac{q}{e}=\frac{144}{1.6\cdot 10^{-19}}=9\cdot 10^{20}[/tex]
