Question

A resistor of 4-ohm resistance and an electric lamp of 20-ohm resistance are connected in series across a 6-volt battery. Draw a labelled circuit diagram by using the symbols for ohm and volt. Calculate:
(a) total resistance of the circuit.
(b) current flowing through the circuit.
(c) potential difference across the resistor.
​(d) potential difference across the electric lamp.

Answer 1

(a) 4-ohm resistance and 20-ohm lamp are connected in series. Hence, the total resistance of the circuit = $4\mathrm{\Omega }+20\mathrm{\Omega }=24\mathrm{\Omega }$

(b) Current flowing in the circuit = $\frac{\mathrm{Voltage}}{\mathrm{Total}\mathrm{resistance}}=\frac{6\mathrm{V}}{24\mathrm{\Omega }}=0.25\mathrm{A}$

(c) The potential difference across the resistor = Current through the resistor $\times$ Resistance = $0.25\mathrm{A}\times 4\mathrm{\Omega }=1\mathrm{V}$

(d) The potential difference across the lamp = Current through the lamp $\times$ Resistance = $0.25\mathrm{A}\times 20\mathrm{\Omega }=5\mathrm{V}$