# Is there any effect of wire's insulation on it's magnetic an

1. Jan 7, 2015

### dumbboy340

Does insulation affect electric and magnetic field?

2. Jan 7, 2015

### Bystander

What's the purpose of insulating a wire?

3. Jan 7, 2015

### dumbboy340

That is what i'm asking.If it does,why a magnet interacts it?i'm confused.please explain it??

4. Jan 7, 2015

### davenn

Insulation does affect the EM propagation speed along the outside of a wire
This becomes very apparent with transmission lines ( antennas) that have either a covering
The result is a slowing of the EM propagation, This is known as the VF -- Velocity Factor

Dave

5. Jan 7, 2015

### davenn

I'm not sure that a magnetic field on its own is affected by insulation
That I would have to research

6. Jan 7, 2015

### Staff: Mentor

Why do you think a magnetic field interacts with insulation? It does not. As stated already, insulation has a higher dielectric constant than air, so it will affect the E field generated by voltages on the wire (including the velocity factor that Dave has mentioned).

7. Jan 7, 2015

8. Jan 8, 2015

### dumbboy340

Thanks!

9. Jan 17, 2015

### TheDemx27

I guess if you're counting a sheath (like in coaxial cable) as the insulation, then it certainly affects the $B$ field produced by the wire because the metal intentionally has high permeability. Otherwise plastic wouldn't have a noticeable effect.