Question

One of the following is not a source of magnetostatic fields (Answer needed with explanation): (a) A de current in a wire (b) A permanent magnet ( c) An accelerated charge (d) An electric field linearly changing with time ( e) A charged disk rotating at uniform speed

Answer 1

Let's check all available options one by one

Explanation:

1. A direct current flowing through a wire produces magnetic field as a inherent property of electric current also as this current is not changing so the magnetic field is also static.
2. A permanent magnet is a natural source of magnetostatics' field .
3. An accelerated charge produces changing electric and magnetic field which further gives rise to propagating electromagnetic field. So this does not produces a static magnetic field and this is our answer.
4. According to Maxwell Hypothesis changing electric field gives rise to static magnetic field.
5. A charged disk while rotating behaves like a current loop carrying current so it also produces a static magnetic field.