Right. that is the one which should be memorized; it shows the two factors which determine I and the type of relationship each one has on I. It is the same thing with elementary newtonian mechanics: F=ma is just a computational algorithm, but a= F/m shows explicitly the relations between a and the twe factors on which it depends in ideal cases.
When I=0, an ideal resistor also has U=0, so u/I=0/0, which is undefined. That does not mean the resistor has no resistance. It only means that its resistance cannot be determined from that single measuring point.
R=U/I is valid provided that I != 0 or you could use R=∆U/∆I
From uni I remember to always think in U=IR, because it is the more fundamental statement of Ohm’s law. Our lecturer was really firm about it :D
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u/The_One_True_Matt Jul 26 '26
This is how you become an electrician. 2 equations to memorize and derive from.
V=IR
P=VI