Question

Electricity problem..... please can you solve this...?

A 6.00V cell produces 0.400A of current when connected to a certain resistor.
(a) How much charge flows out of the cell in 30.0s?
(b) How many electrons flow out of the cell in 30.0s?
(c) How much work does the cell do in 30.0s?

Answer 1

a. `12 C`
b. `7.50*10^19 "electrons"`
c. `72 J`

Explanation:

a. `1 "Amp" = (1 "Coul")/(1 "sec )`

Therefore if you multiply current by time, you get the number of Coulombs.

`"charge" = 0.400 A*30.0 s = -12 C`

b. 1 electron has a charge of -1.60*10^-19 C. So the number of electrons making up that charge of -12 C is given by

`-12 C *(1 "electron")/(-1.60*10^-19 C) = 7.50*10^19 "electrons"`

c. `"Power" = "voltage"*"current"`

Therefore the cell is producing #6.00 V*0.400 A = 2.4 W of power.

The Watt is equal to 1 Joule/second, so this cell is producing `2.4 " Joules"` of energy each second.

In 30.0 s, the total energy the cell gives to the resistor is `2.4 " Joules"*30.0 s = 72 J`. It seems odd to call that work, but the answer is 72 J.

I hope this helps,
Steve