CollegeBoard SAT Physics Study Guide PT1 Q46

CollegeBoard's Book

46) This question asks us to select all the conditions which affect the force on a straight current-carrying wire. In the situation described in the problem, there is magnetic force acting on the wire. There are two formulas for magnetic force.

Where F is force, B is magnetic field, I is current, L is wire length, q is charge, v is velocity, and theta is the angle between either B and L, or between B and v

Choice 1 asks if the strength of the field(B) will change the force(F). This is true because they are directly proportional to each other according to the red and orange equations. Choice 2 asks about the current in the wire. The red equation shows that current(I) is directly proportional to the force(F), so choice 2 is true. Finally, choice 3 asks is the length(L) of the wire will change the magnetic force(F). This is also true; in the red equation, the length(L) of the wire is also directly proportional to force(F). All three conditions are correct.

Answer: E