11. Two parallel wires each carrying the same current (a) repel (b) attract (c) do not experience any force (d) none of the above. 12. A proton entering a solenoid (a) will transit the solenoid unimpeded (b) will follow a helical path (c) will be reflected (d) none of the above. 13. An electron entering a solenoid a) will transit the solenoid unimpeded (b) will follow a helical path (c) will be reflected (d) none of the above. 14. The difference between #13 and #14 is (a) the direction of the orbits , clockwise or counter clockwise, (b) the direction of velocity, left or right, (c) no difference (d) none of the above. 15. Lenz Law (a) does not preserve conservation of energy (b) preserves conservation of momentum (c) preserves conservation of charges (d) prevents unlimited growth of magnetic field by induction. 16. Grasp a current- carrying wire. (a) The direction of the magnetic field around the wire follows the four fingers if the current direction is pointed by the thumb. (a) The direction of the magnetic field follows the thumb if the current direction is pointed by the four fingers. (c) The wire does not generate a magnetic field. (d) None of the above. 17. A single loop generates a magnetic field B at the center. (a) Two loops will double the field. (b) Three loops will triple the field. (c) Four loops will quadruple the field. (d) All of the above