Question

Carefully study the circuit diagram shown below and calculate the value of resistor $x$.

[4 MARKS]

Answer 1

Interpreting data from the circuit: 1 Mark
Steps: 2 Marks
Answer: 1 Mark

Given : EMF = 6V and current in circuit = 0.4A.
As resistors of $12\Omega ,6\Omega and3\Omega$ are in parallel
$\therefore$ Their equivalent resistance,
$\frac{1}{R}=\frac{1}{12}+\frac{1}{6}+\frac{1}{3}\Rightarrow R_1=1.71\Omega$
Equivalent resistance of all the resistors in series, $R=2+1.71+x=3.71+x$
Now, $I=\frac{V}{R}$ [By Ohm's law]
Or $0.4=\frac{6}{3.71+x}$
$\Rightarrow x=11.3\Omega \approx 11\Omega$