0
\$\begingroup\$

In an ideal circuit with just a battery short circuited, where there is no resistance in the wire, why is it necessary to have resistance along the way?

I understand Ohm's Law, and that the current that would flow would be infinitely large.

But the positive charges are flowing from high potential electric energy to low potential electric energy, and as they go, they lower their potential energy, because they get closer to the other voltage terminal, correct? Why is it necessary for the energy to be "spent"?

\$\endgroup\$
3
  • 2
    \$\begingroup\$ Your last paragraph should be a separate question. I'm not sure I understand what you're saying in the first part, either. \$\endgroup\$
    – Hearth
    Jan 28, 2019 at 13:33
  • \$\begingroup\$ It is necessary for energy to be spent so that energy is conserved. The battery is adding energy to the charge carriers, and those carriers return to the lower-energy end of the battery then their energy must go somewhere. Assuming of course that you don't convert energy directly to matter. And for the energy of the carriers to be spent we need something like resistance, which converts electrical energy to heat. \$\endgroup\$
    – Elliot Alderson
    Jan 28, 2019 at 13:43
  • \$\begingroup\$ Since the last paragraph was everything but "in the same note", I'll – in the same spirit as @Hearth's comment – removed that paragraph and would ask you to open a new question and ask it in there (but frankly, the answer is obvious). \$\endgroup\$
    – Marcus Müller
    Jan 28, 2019 at 16:54

2 Answers 2

Reset to default
3
\$\begingroup\$

There's no "need" for a resistor. Remember, a schematic is just a model of reality.

Your model would just be wrong without one, because a battery has internal resistance, and your wire has resistance, too.

Models have validity within a context. Your electric circuit model is only valid within the context of nonrelativistic large-scale electronics in conductors at relatively benign frequencies.

\$\endgroup\$
1
  • \$\begingroup\$ Maybe the question was why there is a need for a resistance SYMBOL? ...Indeed if everybody knows that a battery has resistance why adding a zigzag? \$\endgroup\$
    – Fredled
    Jan 28, 2019 at 17:12
1
\$\begingroup\$

The (first) question is pretty much un-answerable.

A perfect battery maintains a constant voltage across its terminals, regardless of how much current you draw from it. A perfect wire has zero resistance, so there must also be zero voltage from one end to the other.

So if you short a perfect 1.5V battery with a perfect wire, the impossible happens. There is 1.5V across the wire, and 0V across it, at the same time.

In practice, there are no perfect batteries. Superconductors may have zero resistance, but not if you try to pass an infinite current through them.

\$\endgroup\$
1
  • 1
    \$\begingroup\$ I feel like it's wrong to say that a superconductor would stop superconducting with infinite current, but then infinities are funny things. Infinite current density may well exceed the critical magnetic field, though. \$\endgroup\$
    – Hearth
    Jan 28, 2019 at 15:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.