Question

A circuit loop contains a battery of 3.0V connected in series with a parallel combination of two resistor which are a 100 Ohm resistor and an unknown resistor R. The current through the battery is 50 mA. Draw the circuit diagram and find the value of the unknown resistor R

Answer 1

From the ohms law we know that
V = IR
R_equ = V/I
Where V is voltage , I is current in the circuit and R is the equivalent resistanc of the circuit
V = 3 .and I = 50 mA = 50*10^-3 A
R_equ = V/I = 3/(50*10^-3) = 60
Hence the equivalent resistance of the circuit is 60
We know that the equivalent resistance in parallel is
(1/R_equ) = 1/100 + 1/R
1/60= 1/100 + 1/R
1/R = (1/60) - (1/100)
R = 150
hence the unknown resistance will be of 150