Question

Consider two parallel wires carrying current in the same direction. Which one of the following statements is true concerning this situation?
A) The two wires will attract each other, even if no external magnetic field is applied to the wires.
B) The two wires will repel each other, even if no external magnetic field is applied to the wires.
C) The two wires will attract each other only if an external magnetic field is applied to the wires.
D) The two wires will repel each other only if an external magnetic field is applied to the wires.
E) The wires will be neither attracted nor repelled from each other when no external magnetic field is applied to the wires.

Answer 1

Answer:A the two wire will attract each other

Explanation:

When current is flowing in a wire it is surrounded by magnetic field whose direction can be given by right hand thumb rule.

If current is in direction of your thumb then wrapping of fingers will give the direction of magnetic field.

If two wires with current in same direction flows then the combined  magnetic field will be constructive in nature and thus they attract each other.

force on second wire due to first wire is

$F_{21}=I_2\vec{L_2}\times B_1$ which will be towards the first wire