# Open-circuit Req Circuit

Discussion in 'Electronics Homework Help' started by Jermgilbert, Sep 10, 2020.

1. ### Jermgilbert

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Sep 10, 2020
I need assistance with this problem. I cannot seem to figure it out.

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2. ### Jermgilbert

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Sep 10, 2020
I have tried to put it into LTspice, but cannot get it to run. I have tried grounding the open circuit ends, but that doesn't seem to work.

3. ### Harald KappModeratorModerator

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Nov 17, 2011
You need one single ground only. Using multiple grounds will short circuit these parts of the circuit. Show us your LTSPICE diagram or upload the .asc file for inspection.

Provided you get the simulation up and running: how will you determine the equivalent resistance from the simulation?

4. ### Jermgilbert

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Sep 10, 2020
Could I add a resistor at the end of the wires and find the total resistance that way?

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5. ### Harald KappModeratorModerator

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Nov 17, 2011
No.
What is the usual way to determine the resistance of a component? Hint: what is the equation for R = ??? in terms of voltage and current?

6. ### Jermgilbert

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Sep 10, 2020
Oh, alright I could insert a voltage source.

7. ### Harald KappModeratorModerator

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Nov 17, 2011
Good. Where? And what's next?

8. ### Ratch

1,093
334
Mar 10, 2013
Ridiculously simple. Redraw the circuit.

Then use any generic equation solver or pencil and paper to solve the loop equations with a 1 volt source.

1 volt gives 1/25 amp so the resistance is 25 ohms.

Ratch