Question

9. The current in a wire is directed along the y-axis in a uniform magnetic field. The resulting force on the wire is directed along the negative z-axis. The magnetic field is directed along the

   1. +x axis

   2. +y axis

   3. -x axis

   4. -y axis

   5. None of the above.

Answer 1

The answer is that magnetic field will be in direction of negative x axis. Because according to flemmings right hand rule which states that when we stretch our first finger, middle finger and thumb is such a way that they are perpendicular to each other then the first finger will give the direction of magnetic field, middle finger will denote current and the thumb will direct towards the direction of force. So when we apply this rule we see that our first finger points towards the negative x axis and hence that is the correct answer.