Hello All!! Hope you are having a great day.
In the circuit below, when I close the switch, the multi-meter reads 1.7 volts.
When I open the switch, it reads 1.104 volts ( as you can see in the picture)
Can you please tell me why it is 1.104 volts instead of 0 volts? Thank you for your replies.

 

hi Nathan,
I am assuming you are using an actual circuit, not a simulation.???

Is there a strong light falling on the LED.??
Try covering it with your hand.
E

 

Your program can produce such an amazing result for two reasons. The first reason may not be the ideal switch element. When switched off, the resistance may not be infinite (usually in simulators).
The second reason may be that the simulator has a conductivity (albeit very low) from each node to the ground.

 

1. LED1 has capacitance and some voltage presents after S1 is OFF.
2. You need to place S1 in +wire, because now S1 serarates ground from right part of circuit.
It may affects on simulation accuracy.

 

hi Nathan,
I am assuming you are using an actual circuit, not a simulation.???

Is there a strong light falling on the LED.??
Try covering it with your hand.
E

I am simulating it in Multisim. No, there is no light falling on the LED even in the simulation. ( I believe you were trying to tell me that there is some voltage going in reverse from an extraneous light source shining down on the LED).
Ty

 

1. LED1 has capacitance and some voltage presents after S1 is OFF.
2. You need to place S1 in +wire, because now S1 serarates ground from right part of circuit.
It may affects on simulation accuracy.

Could you please retype part 2 of your answer? I dont understand it well. Thank you

 

hi,
As post #3, if its only a simulation, its a sim artefact.
E

 

Your program can produce such an amazing result for two reasons. The first reason may not be the ideal switch element. When switched off, the resistance may not be infinite (usually in simulators).
The second reason may be that the simulator has a conductivity (albeit very low) from each node to the ground.

I think you are correct. The switch did have a resistance of 100M ohms. I changed it to 1000000000M ohms and the voltage is now 2.4 milli volts across the LED. Thanks!

 

Could you please retype part 2 of your answer? I dont understand it well. Thank you

My guess #2 is not proved out.
Guess #1 - charge, stored in LED, released as pulse -27V.

 

I think you are correct. The switch did have a resistance of 100M ohms. I changed it to 1000000000M ohms and the voltage is now 2.4 milli volts across the LED. Thanks!

If you remove one connection to the LED, it should read 0V.