# Magnetic field due to current

Question-
Two proton beams going in the same direction repel each other whereas two wires carrying current in the same direction attract each other. Why does this happen?
Attempt at the solution-
Two proton beams should be equal to two currents in the same direction then why are we getting two different results?

TSny
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For the case of two wires, are the wires electrically charged?

berkeman
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Question-
Two proton beams going in the same direction repel each other whereas two wires carrying current in the same direction attract each other. Why does this happen?
Attempt at the solution-
Two proton beams should be equal to two currents in the same direction then why are we getting two different results?
There is a difference between a beam of protons (or electrons) and a current in a wire. Can you think of what the difference is?

There is a difference between a beam of protons (or electrons) and a current in a wire. Can you think of what the difference is?
For the case of two wires, are the wires electrically charged?
The wires are not charged as electrons are continuously flowing through them. The only difference between the two cases is that in one case electrons are enclosed in a conductor and in the other they aren't.
I find this question too confusing. What is the reason?

TSny
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The wires are not charged as electrons are continuously flowing through them.
OK, so each wire has essentially zero net charge. What about the proton beams?

OK, so each wire has essentially zero net charge. What about the proton beams?
The protons are continuously flowing without any obstruction in the beam as well. So I think the net charge on the beam should be zero too. Please correct me if I'm wrong.

TSny
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A proton beam is just a stream of protons. Does each proton carry any net charge?

A proton beam is just a stream of protons. Does each proton carry any net charge?
Yes each proton carries a net charge.But so does an electron. So if the stream of moving protons is considered charged, applying the similar logic the wire should also be considered charged. Is there any difference in the two cases?

TSny
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What type of electrically charged particles are inside a piece of wire?

• physicsmaths1613
What type of electrically charged particles are inside a piece of wire?
Electrons, which are flowing just the same way as in a beam

TSny
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Only electrons? Any other type of electrically charged particles inside the wire (that are not flowing)?

• physicsmaths1613
Only electrons? Any other type of electrically charged particles inside the wire (that are not flowing)?
Oh! I think I got your point. Beams have a net charge as they have only let's say electrons . so they repel due to electrostatic force. Whereas a wire is neutral due to the presence of both electrons and protons. So they is no electrostatic repulsion. Only attraction exists due to moving electrons and the magnetic field of the other wire.
Please point out my errors if any.
And one more question. Does the force of repulsion between the beams overpower the attraction due to magnetic field in between the beams resulting in net repulsion?

TSny
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Oh! I think I got your point. Beams have a net charge as they have only let's say electrons . so they repel due to electrostatic force. Whereas a wire is neutral due to the presence of both electrons and protons. So they is no electrostatic repulsion. Only attraction exists due to moving electrons and the magnetic field of the other wire.
Please point out my errors if any.
That's correct.
And one more question. Does the force of repulsion between the beams overpower the attraction due to magnetic field in between the beams resulting in net repulsion?
Yes. Good.

• physicsmaths1613
That's correct.

Yes. Good.
Thank you so much for helping me figure out the answer myself!!