Understanding Circuit Resistance: Debunking the Myth of Zero Ohms

  • Thread starter Thread starter forte74
  • Start date Start date
  • Tags Tags
    Circuit
AI Thread Summary
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
Messages
4
Reaction score
0
if i just measure the resistance btw L and N , the resistance should be zero right, then how can it be 0.3 ohms ?
 

Attachments

  • howcanitshow0.3ohms.PNG
    howcanitshow0.3ohms.PNG
    54.3 KB · Views: 474
  • why0.3ohms.PNG
    why0.3ohms.PNG
    49.2 KB · Views: 441
  • whyisthis0.3ohmsthisnotacompletepaht22.PNG
    whyisthis0.3ohmsthisnotacompletepaht22.PNG
    57.2 KB · Views: 482
  • whyisthis0.3ohmsthisnotacompletepaht223.PNG
    whyisthis0.3ohmsthisnotacompletepaht223.PNG
    57.2 KB · Views: 448
Engineering news on Phys.org
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
 
Last edited by a moderator:
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?
 
I have recently moved into a new (rather ancient) house and had a few trips of my Residual Current breaker. I dug out my old Socket tester which tell me the three pins are correct. But then the Red warning light tells me my socket(s) fail the loop test. I never had this before but my last house had an overhead supply with no Earth from the company. The tester said "get this checked" and the man said the (high but not ridiculous) earth resistance was acceptable. I stuck a new copper earth...
Thread 'Electromagnet magnetic field issue'
Hi Guys We are a bunch a mechanical engineers trying to build a simple electromagnet. Our design is based on a very similar magnet. However, our version is about 10 times less magnetic and we are wondering why. Our coil has exactly same length, same number of layers and turns. What is possibly wrong? PIN and bracket are made of iron and are in electrical contact, exactly like the reference design. Any help will be appreciated. Thanks. edit: even same wire diameter and coil was wounded by a...
Thread 'Beauty of old electrical and measuring things, etc.'
Even as a kid, I saw beauty in old devices. That made me want to understand how they worked. I had lots of old things that I keep and now reviving. Old things need to work to see the beauty. Here's what I've done so far. Two views of the gadgets shelves and my small work space: Here's a close up look at the meters, gauges and other measuring things: This is what I think of as surface-mount electrical components and wiring. The components are very old and shows how...
Back
Top