Question

how many electrons passes through a 20 ohm resistor through 10 mins if there is a drop of 30 volts a cross it

Answer 1

From Ohm’s Law

$V=IR \\ I=\frac{V}{R}= \frac{30 \;V}{20} = 1.5 \;A \\ I= \frac{Q}{t} \\ Q=It = (1.5 \;A) \times (10 \times 60 \;s) = 900 \;C \\ Q=ne \\ n= \frac{Q}{e} = \frac{900 \;C}{1.6 \times 10^{-19} \;C}=562.5 \times 10^{19}$