0
\$\begingroup\$

I've learn some electronic knowledge at school and so confused by some questions.

Q1. IS it possible a flow of electricity without an electric field?

Q2. I've learn that moving of particle with electric charge in electric field makes potential difference. Then, let's suppose no resistance in wire. IF Q1 is true, wire with a flow of electricity makes an electric field, and in the electric field, an electron moves. Then potential difference must exist. But when measured, there is no potential difference. ( I learn there is ESR in battery, but I wonder whether moving of electron dosen't make any potential difference or not.)

Sorry for my bad English, but I hope someone could help me to find answer.

\$\endgroup\$
1
\$\begingroup\$

Q1. IS it possible a flow of electricity without an electric field?

If you mean is it possible to have flow of electricity that's not caused by an electric field, consider Millikan's oil drop experiment, before the external electric field is applied. Ions attached to drops of oil flow downward due to gravity acting on the oil drops. That's a (very tiny) current caused by gravity rather than by an electric field.

But there were of course electric fields present during the experiment since each ion produces a field of its own.

Q2. I've learn that moving of particle with electric charge in electric field makes potential difference.

That doesn't sound right. Read my answer to another recent question for a clarification about why the potential difference is present even when there's no mobile charge present for the electric field to act on.

Then, let's suppose no resistance in wire. IF Q1 is true, wire with a flow of electricity makes an electric field, and in the electric field, an electron moves. Then potential difference must exist. But when measured, there is no potential difference.

The solution to this is to realize that (leaving aside superconductivity) no wire with 0 resistance actually exists. So every real wire has at least a small resistance, and if there's a current in the wire, then a small electric field must be present there to make that current flow.

We should only make the ideal wire approximation when the resistances in the wires of a circuit are much less than the resistances of other elements in the circuit, so that considering the wire resistance would complicate understanding of the circuit behavior without changing that behavior appreciably.

\$\endgroup\$
  • \$\begingroup\$ @Photon Then, when the mobile charge moves in the wire, isn't there any potential difference? One more question,I don't know how current flows (direct transfer of charge? or transfer of energy by vibration???) \$\endgroup\$ – dongho Aug 21 '17 at 3:02
  • \$\begingroup\$ @dongho, there is a potential difference across a wire with current flowing. But the potential difference can be very small and still produce a substantial current. So small that we can ignore it relative to other drops in the circuit. \$\endgroup\$ – The Photon Aug 21 '17 at 4:36
  • \$\begingroup\$ For your second question, current flows when charge moves. But, for example, a particular electron doesn't have to move from one end of the wire to the other before energy can be transferred. \$\endgroup\$ – The Photon Aug 21 '17 at 4:39
  • \$\begingroup\$ @Photon I think when current flow in wire, the charge moving in wire causes electronic field and there must be potential difference. But, according to your words, current could flow without moving charge. Then, how the potential difference could be explained? \$\endgroup\$ – Yelim Aug 21 '17 at 8:26
  • \$\begingroup\$ 1. In a wire, there are both mobile carriers (electrons) and fixed carriers (protons) in the nuclei of the atoms. Since they are equal in number, they do not produce a macroscopic field. The current in a wire flows because of a field imposed by some other device, like a battery 2. What part of "current flows when charge moves" makes you think I am saying current can flow without charge? \$\endgroup\$ – The Photon Aug 21 '17 at 14:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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