# I Why won't a magnet exert a force on a stationary charged particle

1. May 17, 2016

### d4rr3n

Why is it that a static electric field will exert a force on a stationary charged particle but a magnetic field from a permanent magnet will not?

I am somewhat confused by this because the magnetic field in a permanent magnet is the result of spin charge polarisation which must generate closed electric field lines which wraparound the bar magnet at right angles to the magnetic field.

If we think about an electromagnetic we have electrons flowing through a wire so there is charge which must generate electric field lines again at right angles to the magnetic field. why is it these electric field lines exert no force on a stationary charged particle?

What's different about the nature of these electric fields that one will exert a force on a stationary charged particle but the other wont?

2. May 17, 2016

### Khashishi

No, permanent magnets do not create closed electric field lines that wrap around the magnet. A changing magnetic field generates an electric field, but a static magnetic field (of a magnet) will not generate an electric field.

3. May 17, 2016

### d4rr3n

So the current flowing through the wire of an electromagnet generates no electric field?

4. May 17, 2016

### DrewD

Khashishi answered for permanent magnets. For an electromagnet, there will be no closed electric field lines outside of the wire coils. It is essentially the same if you are viewing it completely outside of the material.

Remember, electric current is a flow of electric charges, but the net charge is still 0. Electrons aren't added to the wires, just pulled through the coils.

5. May 17, 2016

### Staff: Mentor

A closer analogy is the current flowing through a superconducting loop. Those indeed generate no electric field.

6. May 18, 2016

### houlahound

But a wire has resistance hence there is an electric field set up because there is a voltage drop ie;

Vwire = Iwire X Rwire

7. May 18, 2016

### Staff: Mentor

That is precisely what makes a superconducting wire a better analogy for a permanent magnet than a resistive wire. Neither a superconducting wire nor a permanent magnet have an electric field around the current loop.

Of course, it is just an analogy, so it isn't perfect, but it does clearly show that you can have current without E fields.

8. May 18, 2016

### Leesa Johnson

Yes, When an emf is induced in the coil than a dynamic field is generate it will create a magnetic field that will cause to generate moving particle and these particles attract stationary particle and they will start to moving in the magnetic field.

9. May 18, 2016

### Drakkith

Staff Emeritus
I'm sorry, Leesa, but I'm having trouble understanding what you've said here.