Question

If the current in a wire increases from 5 A to 10 A, what happens to its magnetic field? If the distance of a charged particle from a wire changes from 10 cm to 20 cm, what happens to its magnetic field? If the charge of a particle changes from 2 µC to –2µC, what happens to the force exerted on that particle?

Answer 1

(1) Doubling of the current through the wire will result in doubling of its magnetic  field.

The magnetic field around a wire is a function of the current I and radial distance r

$B = \frac{\mu\cdot I }{2\pi r}$

(with mu denoting the magnetic permeability of the medium). So, B is directly proportional to I. The field magnitude will double with the doubled current from 5A to 10A

(2) Using the same formula as in (1), we can see that the magnetic field is inversely proportional to the radial distance from the wire. So, a particle at 20cm will experience half the magnitude compared to a particle at 10cm.

(3) Answer

If a particle with a charge q  moves through a magnetic field B with velocity v, it will be acted on by the magnetic force

$F_m = B\cdot v\cdot q$

So, a particle with charge -2uC will experience a magnetic force of same magnitude but opposite direction (and perpendicular to B) as compared to a particle with a charge of 2uC

Answer 2

Answer:

1.) The field is twice as strong

2.) The field is half as strong

3.) The force is reversed

Explanation: