Two long wires each carrying a d.c current in the same direction are placed close to each other. Which one of the following statements is correct?

CONCEPT:

Magnetic field:

• The space or region around the current-carrying wire/moving electric charge or around a magnet in which force of magnetism can be experienced by other magnetic material is called as magnetic field/magnetic induction by that material/current.
• It is denoted by B.

The magnetic force per unit length between two parallel wires is given by;

\(F = \frac{{{\mu _{0\;}}{I_1}\;{I_2}}}{{2\pi \;d}}\)

Where μ₀ is the permittivity of free space, I₁ is d.c current in first wire and I₂ is d.c current in second wire and d is the distance between two wires.

EXPLANATION:

• When two wires carrying a d.c current are placed parallel to each other then there always will be a magnetic force acting between two wires. So options 3 and 4 are wrong.
• When the current flowing in the wires are in the same direction then the force between two wires is attractive. So option 1 is correct and option 2 is wrong.
• When current is in opposite direction then force is repulsive.