Question

In the circuit shown in Fig., find the reading of the ammeter A when the switch S is closed.

Answer 1

When the switch is closed, resistance 60 Ω gets connected to the circuit.

Thus, in the circuit the parallel combination of 60 Ω and 200 resistors is connected in series with the 5 Ω resistor.

∴ Resistance in parallel,

`1/R_P = 1/60 + 1/20`

= `(1 + 3)/60`

= `4/60` Ω

or `R_P = 15 Ω`

Now, total resistance of the circuit = 15 + 5

= 20 Ω

Current through the circuit,

I = `V/R`

= `10/20`

= 0.5 A

The reading of the ammeter is thus 0 .5 A, when the switch is closed.