As an example of the magnetic field acting on the current-carrying conductor, put two current-carrying straight wires parallel together. The experiment shows that if the current direction of the two straight lines is the same, they attract each other. On the contrary, if the current direction of the two current-carrying wires is opposite, they repel each other.
The reason for this phenomenon is that two current-carrying straight wires should receive the effect of each other's electromagnetic force, and the direction of this electromagnetic force can be determined by the left-handed rule
The bus bars (busbars) in power plants, substations and distribution rooms of factories are parallel current-carrying straight conductors. In order to ensure that the bus has sufficient mechanical strength, an insulating pole is often installed at a certain distance to prevent the damage caused by the huge electromagnetic force generated by the excessive short circuit current in case of short circuit. In addition, the electric measuring instrument also works according to the principle that the energized conductor is subjected to electromagnetic force in the magnetic field.