A series circuit contains a 9-volt battery, a 3-ohm resistor and a 2-ohm resistor. What is the voltage drop across the 2-

ohm resistor?

Answer: V r 2 = 3.6 V Explanation: There is a voltage divider equation for two resistors in series:

V r 2 = R 2 R 1 + R 2 V

Because you can, arbitrarily choose which resistor you designate as R 2 and the other as R 1, you can use this to find the voltage across either resistor. In your case, you want to designate the 2 Ω resistor as R 2:

V r 2 = 2 Ω 3 Ω + 2 Ω 9 V V r 2 = 3.6 V