What is the effect of an open switch in a circuit?

An open switch in a circuit creates a break in the path through which electric current flows. When the switch is open, there is no complete circuit, and as a result, the flow of electricity is interrupted. This means that any devices connected in the circuit, such as light bulbs or motors, do not receive power and cannot operate. Therefore, the circuit is effectively turned off when the switch is open.

In contrast, a closed switch would complete the circuit, allowing current to flow and enabling the devices to function. The other options do not apply in this case, as an open switch does not activate the circuit, increase current, or light up a bulb.