In an electric circuit shown, each cell has e.m.f. $2 V$ and internal resistance $1 Ω$ . The external resistance is $2 Ω$ . The value of current (in A) is

Question

In an electric circuit shown, each cell has e.m.f. 2 V and internal resistance 1 Ω . The external resistance is 2 Ω . The value of current (in A) is

TestHub · Accepted Answer

From the given circuit diagram, three cells are connected in series.

By observing the symbols of the cells, all three cells are oriented in the same direction (the longer line representing the positive terminal is on the left for each cell). Therefore, their electromotive forces (e.m.f.) will add up.

Total e.m.f. of the combination, $E_{e q} = E_{1} + E_{2} + E_{3}$
$E_{e q} = 2 V + 2 V + 2 V = 6 V$

The internal resistances of the cells are also in series.
Total internal resistance, $r_{e q} = r_{1} + r_{2} + r_{3}$
$r_{e q} = 1 Ω + 1 Ω + 1 Ω = 3 Ω$

The external resistance in the circuit is $R = 2 Ω$ .

The total resistance of the circuit is the sum of the external resistance and the equivalent internal resistance:
$R_{t o t a l} = R + r_{e q} = 2 Ω + 3 Ω = 5 Ω$

The current $I$ flowing through the circuit is given by Ohm's law:
$I = \frac{E _{e q}}{R _{t o t a l}}$
$I = \frac{6}{5} A = 1.2 A$

Answer: $1.2$

Physics - Current Electricity Question with Solution | TestHub

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