physics direction of force

Question

Say that the following is true. A long straight wire carries a current from top to bottom down the center of this page. A magnetic field points from left to right across the page. The force on the wire would

a. point left.

b. point right.

c. point into the page.

d. point out of the page.

e. be zero.

Answer 1

To figure out the direction of force on the wire we need to consult the following equation: F=IL×B. In this equation, I is the current, L is the length of the wire, and B is the magnetic field. The × in the middle is not regular multiplication but rather the cross product (or vector product). Using the right hand rule associated with cross products, we point our fingers in the direction of the current and then curl them in the direction of the magnetic field. Whichever way your tumb points is then the direction of the force. Doing this demonstrates that the force felt by the wire points out of the page. Therefore, the correct answer is d.