Question

A straight wire is carrying an electric current :

• A. There are no magnetic lines of force near the wire
• B. There are lines of force and they are circular lines encircling the wire
• C. The lines of force are straight lines parallel to the wire and in the direction opposite to the current
• D. The lines of force are straight lines parallel to the wire in the direction opposite to the current.

Answer 1

Answer: (B)

There are lines of force and they are circular lines encircling the wire

The direction of line of forces of magnetic field produced by a current carrying wire can be obtained by using maxwell's right hand thumb .By holding the thumb along the the direction of current then the direction in which your finger encircle the wire will give the direction of magnetic line of forces .