What happens when a switch in a circuit is open?

What happens when a switch in a circuit is open?

• A. No current flows; the circuit is broken
• B. Current flows normally
• C. Voltage increases
• D. Resistance becomes zero

Answer: (A)

Opening the switch breaks the path that current must follow, so no current can flow. Current only travels in a complete loop; with the switch open there is an air gap and the circuit’s path becomes effectively infinite in resistance, which means I = V/R gives zero current. The source voltage still exists across the gap, but it cannot push current through because there’s no continuous conductor to complete the circuit. So the situation is described by no current flowing. The other ideas don’t fit: there isn’t a normal flow of current until the circuit is closed, the voltage doesn’t automatically rise because the switch is open, and the resistance doesn’t drop to zero—instead it acts as an open circuit with very high resistance.

Opening the switch breaks the path that current must follow, so no current can flow. Current only travels in a complete loop; with the switch open there is an air gap and the circuit’s path becomes effectively infinite in resistance, which means I = V/R gives zero current. The source voltage still exists across the gap, but it cannot push current through because there’s no continuous conductor to complete the circuit. So the situation is described by no current flowing. The other ideas don’t fit: there isn’t a normal flow of current until the circuit is closed, the voltage doesn’t automatically rise because the switch is open, and the resistance doesn’t drop to zero—instead it acts as an open circuit with very high resistance.