Question

Draw the circuit diagram of an electric circuit containing a battery of 6 V, a key, an ammeter, a resistor of 4 Ω in series with a combination of two resistors of 8 Ω each in parallel, and a voltmeter across the parallel combination.
(a) Calculate the resistance of the circuit.
(b) Find the current flowing in the circuit.
(c) What will be the voltage across the parallel combination of resistors?

Answer 1

(a) In the circuit, there is a 4-ohm resistor in series with the parallel combination of two 8-ohm resistors.

Total resistance of parallel combination = $\frac{8\times 8}{8+8}=\frac{64}{16}=4\text{Ω}$

So, net resistance of the circuit = $4\text{Ω +}4\text{Ω = 8}\text{Ω}$

(b) Current in the circuit = $\frac{\mathrm{Voltage}}{\mathrm{Net}\mathrm{Resistance}}\text{=}\frac{6\text{V}}{8\text{Ω}}\text{= 0.75 A}$

(c) The voltage across the 4-ohm resistor = $0.75\text{A × 4 Ω= 3 V}$

So, the voltage across parallel combination = $6\text{V - 3 V = 3 V}$