2(iii)
In the below circuit diagram, calculate:
(a) the external resistance of the circuit.
(b) the current I2.
(c) the current I.

Show SolutionHide Solution↓
(a) 12Ω and 8Ω are in parallel.
$\frac{1}{\text{R}}$ = $\frac{1}{12}$ + $\frac{1}{8}$ = $\frac{2+3}{24}$ = $\frac{5}{24}$
So the equivalent resistance = $\frac{24}{5}$ = 4.8Ω
2Ω is in series with this combination.
Hence the total resistance = 2 + 4.8 = 6.8Ω
(b) Potential difference across the 12Ω resistor = potential difference across 8Ω resistor
Or, 12 × 0.4 = 8 × I2
∴ I2 = $\frac{12 × 0.4 }{8}$ = = 0.6 A
(c) Current I = I1 + I2 = 0.4 + 0.6 = 1 A