Question

Calculate the total number of electrons flowing through a circuit in 20 mins and 40 s, if a current of 40 μA flows through the circuit.
[1 e^– = 1.6 × 10^-19 C]

Answer 1

Number of electrons = n = ?

Time = t = 20 min 40 s

t = (20 × 60 + 40) s

t = 1240 s

Electric current = I = 40 μA

I = 40 × 10^-6 A

Charge on one electron = 1 e = 1.6 × 10^-19 C

Charge = Q = ?

I = `"Q"/"t"`

Q = It

Q = 40 × 10^-6 × 1240

Q = 49600 × 10^-6 C

Q = 4.96 × 10^-2 C

Now Q = n (charge on 1 electron) = ne

4.96 × 10^-2 = n × 1.6 × 10^-19 

n = `(4.96 xx 10^-2)/(1.6xx10^-19)`

n = 3.1 × 10¹⁷ electrons