The correct answer to the question is option 1: The wires will attract each other.
When two long wires carrying a direct current (d.c.) in the same direction are placed close to each other, they experience a force of attraction. This phenomenon is known as Ampere`s force law.
Ampere`s force law states that two parallel conductors carrying currents in the same direction will exert an attractive force on each other. This force is a result of the magnetic fields produced by the currents in the wires.
To understand this, we can consider the magnetic field produced by one wire. The magnetic field lines form concentric circles around the wire. When another wire is placed nearby, the magnetic field produced by the first wire exerts a force on the charges in the second wire, causing the wires to attract each other.
It is important to note that this force of attraction exists continuously as long as the current is flowing in the wires. It is not just limited to the moment when the current is switched ON or OFF (as stated in option 4).
Therefore, the correct statement is that the wires will attract each other. Option 2 (the wires will repel each other) and option 3 (there will be no force between the wires) are incorrect.