Two parallel wires are carrying current. If the currents are in the same direction, what is the interaction between the two wires and why? How would this be different in the currents were in opposite directions?
Same direction: I = I1 + I2.
Opposite direction: I = I1 - I2.
When two parallel wires carry currents in the same direction, they experience an attractive force between them. This force is known as the Ampere's Law force. To understand why this happens, you can use the right-hand rule for current-carrying wires.
If you point your right thumb in the direction of the current in one wire, and wrap your fingers around the wire, the magnetic field lines created by the current will be in a clockwise direction. Similarly, if you repeat this process for the other wire, the magnetic field lines will be in the same direction.
According to the right-hand rule for magnetic fields, when two parallel wires carry currents in the same direction and their magnetic field lines align, the wires experience an attractive force. This happens because the magnetic fields generated by the currents interact with each other.
On the other hand, if the currents in the parallel wires are in opposite directions, the wires experience a repulsive force. Again, using the right-hand rule, if the magnetic field lines created by one wire point clockwise and the other wire points counterclockwise, their magnetic fields will oppose each other. As a result, the wires repel each other due to the interaction of their magnetic fields.
In summary, when currents in parallel wires are in the same direction, they attract each other due to the alignment of their magnetic fields. When the currents are in opposite directions, they repel each other because their magnetic fields oppose each other. This understanding is based on the right-hand rule and the principles of magnetism and electromagnetic interactions.