Figure shows two perpendicular wires carrying the same current. In which of the following cases, there will not exist even one point at finite distance where magnetic field is zero.
Select all that apply

Question

Figure shows two perpendicular wires carrying the same current. In which of the following cases, there will not exist even one point at finite distance where magnetic field is zero.

G1 Physics · Accepted Answer

For two perpendicular long wires, cancellation requires equal magnitudes μ₀I/(2πr₁)=μ₀I/(2πr₂) and opposite directions. Applying the right-hand rule to each current orientation shows that finite zero-field points exist only in case C; therefore the cases with no finite zero point are A,B,D.