Question

What happens to a circuit when the switch is off?
(A) The circuit is complete
(B) The circuit is now an open circuit
(C) Electricity flows continuously
(D) Electricity flows discontinuously

Answer 1

Hint: A switch in an electric circuit has 2 states. One of them is open state and the other is known as closed state. Open state means that it is not connected or, the connection is not complete and is hence open. In this state no current passes. The other state is known as the closed state, in this the connection is closed and current flows through the circuit.

Complete step-by-step solution

In a circuit a cell is connected along with a switch which provides constant current in the circuit. So when the switch is turned off the current flow does not happen because the charges are not moving. No electricity is flowing in that particular circuit and is expected to flow only in a closed circuit.
























Since no current flow is observed in the circuit when the switch is turned off the circuit is called an open circuit.

The correct option is B - The circuit is now an open circuit.

Note

(A) In the open circuit:
1. Current through the circuit is zero
2. Potential difference between at the open is E
3. Potential difference at components is zero

(B) In closed circuits:
1. Current is given by $I = \dfrac{E}{{R + r}}$
2. Potential difference is \[V = IR\]
3. Power dissipated in external resistance is \[{I^2}R\]
4. Internal resistance of the cell is $r = \left( {\dfrac{E}{V} - 1} \right)R$