15. Two parallel wires carry currents in opposite directions. What is the direction of the magnetic force on current I1, due to current I2?
(A) Left
(B) Right
(C) Top the page
(D) Bottom the page
(E) Out of the page
16. An electron enters a uniform electric field perpendicular to the field lines. What must be the direction of the magnetic field in order to cancel the electric force effect?
(A) Left
(B) Right
(C) Top the page
(D) Into the page
(E) Out of the page
17. An electron enters a uniform electric field perpendicular to the field lines. What is the magnitude of the magnetic field if the electric effect completely canceled?
(A) Ev
(B) v/E
(C) zero
(D) E/v
(E) eEv