Understanding Circuit Resistance: Debunking the Myth of Zero Ohms

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Measuring resistance between Line (L) and Neutral (N) in a circuit should ideally yield zero ohms, but readings of 0.3 ohms can occur due to the source impedance being in parallel with the circuit impedance. This discrepancy indicates that the circuit is not completely isolated, as even when the black wire is unplugged, some resistance can still be measured. It's important to ensure that measurements are taken with the circuit disconnected from the power source for accuracy. The circuit's functionality, such as whether the bulb shines or not based on switch positions, also confirms proper operation. Understanding these concepts is crucial for effective troubleshooting in electrical circuits.
forte74
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if i just measure the resistance btw L and N , the resistance should be zero right, then how can it be 0.3 ohms ?
 

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forte74 said:
if i just measure the resistance btw L and N , the resistance should be zero right, then how can it be 0.3 ohms ?

What information are you given about the source impedance for the AC Mains feed of Line and Neutral into this circuit? The source impedance is in parallel with the circuit impedance.

Is this for schoolwork? If so, I will move your posts to the Homework Help forums.
 
im using the software for Troubleshooting Electrical circuits by BNN. studying this to get prepared as electrician. for if you look at the last 2 pictures, you can see that you can still get 0.3 ohms if the black wire is unplugged
 
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I guess by zero resistance you mean infinite resistance. And does the circuit work as it should (all switches on - bulb shines, at least one off - bulb off). I hope, you measure it when you have the circuit disconnected from power source. And by the way, you measure on real circuit or are we still talking about that SW?
 

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