At t = 0 a charge q is at the origin and moving in the y-direction with velocity 𝑣 = 𝑣ĵ. The charge moves in a magnetic field that is for y 0 out of page and given by B1ẑ and for y

Question

At t = 0 a charge q is at the origin and moving in the y-direction with velocity 𝑣 = 𝑣ĵ. The charge moves in a magnetic field that is for y > 0 out of page and given by B1ẑ and for y < 0 into the page and given -B2ẑ. The charge's subsequent trajectory is shown in the sketch. From this information, we can deduce that

G1 Physics · Accepted Answer

The sense of curvature at entry fixes q>0 from qv⃗×B⃗. Since r=mv/(|q|B), the smaller-radius segment corresponds to the larger field; the sketch gives |B₁|<|B₂|. Hence A.