Voltage across an open switch

Thread Starter


Joined Jun 8, 2009
Hello I was wondering if we had a circuit with an open switch, what would the voltage be across the (SWITCH).

thank you


Joined Aug 9, 2008
hi fahadali,

I think it would depend on the circuit.If its a simple series circuit with a resistor connected across a voltage source then the supple voltage is the voltage across the open circuit.You can consider the open switch as infinte resistance and by apply voltage division rule almost all the source drops across the open switch.In the case of complex circuits i think you can find the thevenin's equivalent voltage which would be the voltage across the switch.


Joined Mar 1, 2008
The voltage across an open switch will be the same as the circuit Vcc.

The voltage across a closed switch will be zero volt (or close to zero) depending on the internal resistance of the switch contact. A closed switch can be seen as a simple piece of wire, with basically no volt drop across the terminals.