Question

If a current I is flowing in a straight wire parallel to x-axis and magnetic field is there in the y-axis then, ______.

Options

• the wire experiences no force

• the wire experiences force in y-direction

• the wire experiences force in z-direction

• the wire experiences force in x-direction

Answer 1

If a current I is flowing in a straight wire parallel to x-axis and magnetic field is there in the y-axis then, the wire experiences force in z-direction.

Explanation:

Force experienced by a conductor of length l carrying current I placed in magnetic field B is given by

`vec"F" = "I"vecl xx vec"B"`. Now,

`"I"vecl = |"I"vecl| hat"i"` and `vec"B" = |vec"B"|hat"j"`

Thus, `vec"F" = "I"vecl xx vec"B" = |"I"vecl|hat"i" xx |vec"B"|hat"j" = "I"l"B" (hat"i" xx hat"j") = "I"l"B" (hat"k")`

The force acts along the positive z-axis.