Hi Claude,

your son is right, sorry for the mistake (I'm a computer scientist so physics was only course material for me). I looked at the fourth Maxwell's equation on electromagnetism and indeed, a magnetic field (B) depends on (the first derivative of) the electric field (E), and the

current_intensity * permeability_of_free_space.

This leads to something called Ampere's law that (after integration) shows:

permeability_of_free_space * I
B = -------------------------------
2 * PI * R

(B) is the magnetic field generated by the current (I) on a circle perpendicular on I, with radius (R).

Assuming
R = 1 meter
I = 1 Ampere
permeability_of_free_space = 4*PI*10_to_(-7)

we see that B = 2 * 10_to_(-7) Tesla (using MKS)

comparing this to the value of the earth magnetic field (~0.5 * 10_to_(-4))it seems that (B)in the car is relatively smaller (hundreds of times). However, a magnetic field also generates an electic field (E), as stated in the second Maxwell's equation. To compute (E) in the car is harder and I can't remember it on top of my head.

Sorry again,
Serban

PS. The numbers I derived for (B) are based on some assumptions, and may be different than what we really have in the car. How different? Don't know.