Uncovering the Physics Behind Everyday Phenomena

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What's the physics behind it?
 
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Color coded so you know which is which.
 


Consistency, polarity convention.

This way, you can compare to voltages and know whether they are both the same polarity or not, e.g., they are 100V and 150V, or 100V and -150V.
 


I think it's the other way round. We usually connect the red cable to the positive terminal and the black to the negative.
 


Gordianus said:
I think it's the other way round. We usually connect the red cable to the positive terminal and the black to the negative.

You beat me to it :) yes exactly. I am a bit suprised the first 2 responders didnt pick up on that one lol

Dave
 


Gordianus said:
I think it's the other way round. We usually connect the red cable to the positive terminal and the black to the negative.
I agree. And the only reason I can think of is that you would prefer to have a positive number for the meter reading. But it really isn't necessary; if you reverse the leads you just get -1 times the reading you would have gotten.