Question

A brty of 9V is connected in series with resistance of O.2 /0.3 /0.4/0.5 and 12 ohm resp. how much current would flow through the 12 ohm resistor?

Answer 1

When connected in series the current through all the resistances is same and the equivalent resistance is the sum of all the resistances. The current in the circuit is equal to V/R, R being the equivalent resistance.
R = .2 + .3 + .4 + .5 + 12 = 13.4 Ohm
I = V/R = 9/13.4 = 0.67 A
This is the current through all the resistances including the 12 Ohm resistance.