0

Consider two points A and B in a circuit which have no resistance between them. If we assume current flows through the part AB from A to B, then that means there must be a nonzero potential difference between the points A and B. But as a contradiction, since there's no resistance in the part AB, no voltage is lost while going from A to B, meaning the potential difference must be 0. I don't understand where my mistake is?

On a similar note, when a part of a circuit is earthed, why does the potential of that part become 0?

Arxd
  • 59
  • 3

1 Answers1

0

That’s good question!

The voltage you apply has nothing to do with the resistance of the circuit. The potential energy at the point B is lower than at the point A which in the lack of resistance leads to particles getting this potential energy being transformed into other forms of energy, e.g. kinetic energy. Here we assumed conservation of energy since the lack of resistance would mean lack of scattering. Resistance usually comes from the scattering of the charged particles off each other or elements of the media through which the particles are moving.

As the simplest example one can consider electrons being accelerated through a vacuum when applying a voltage difference. There is no resistance yet there is a voltage difference.

About the last question: potential energy is a relative value meaning that by itself it doesn’t tell us anything. It’s only the difference of the potential energy that we can measure. So, for convenience people usually set the earthed part to be 0 and measure all other potentials in the circuit with respect to the earthed part.

AZH
  • 1