Another Current and Drift Velocity Question

[predentalgirl1]

[SOLVED] Another Current and Drift Velocity Question

1. A car's starter motor draws 50 A from the car's battery during startup. If the startup time is 1.5 s, how many electrons pass a given location in the circuit during that time?







3.As current = rate of flow of charge,
I = q/t
Charge, q = I.t = 50 x 1.5 = 75 C
1 electron has charge, e = 1.6x10^-19 C
And q = N.e
Number of electrons which pass in 1.5 s,

N = q/e = 75 C/1.6x10^-19 C = 4.69x10^20 electrons


OR use this equation:I = ne/dt and get:



n = 50 x 5 = 250
e 1.6 x 10-19
= 156.25 x 10^19
= 1.56 x 10^21 electrons
1.56 x 10^21 electrons pass during that time.

Which solution/answer is correct?

 

[TVP45]

It would be better if you used units. I'm not sure I understand your numbers.

In the second equation, what is the 5 in n=50 x 5?

 

[quantumdude]

The first method is correct. I'm afraid I don't understand the second one. What's "d" in that equation?