Question

Any help is good ^.^ When connecting a switch in a series with a 75-W bulb to a 120-V power source, what would be the potential difference across the switch when it is turned on and when its turned off??

Answer 1

On the condition that the potential difference across the open switch is measured with a very high impedance voltmeter, the potential difference across the open switch will be very close to 120 V.
When the switch is closed, the potential difference across the switch will depend on the contact resistance of the switch. A theoretically perfect switch would have zero contact resistance and the potential difference across the closed switch woulf be zero.

Answer 2

Thanks! But an open switch is when its turned off and a closed switch is when its turned on, correct? @kropot72

Answer 3

@J.Velasquez You are correct. Please note correction: ".....the closed switch would be zero."

Answer 4

Okay, thanks again(: