The force of attraction and repulsion between magnetic poles becomes greater when stronger magnets are used. you can see this if you attach a spring to the bar magnet in such a way that the spring will have no tension when the norths poles of the two magnets are as close as possible to the south poles of the horseshoes magnet. 

With the spring attach it will turn only party way, to a position where its turning force is balanced by the force on the spring. if you were to replace the bar magnet, the force of repulsion between the like poles would be greater and the bar magnet would turn further against the force of the spring. 

If you remove the bar magnet and replace it with a coil of wire, you have a galvanometer. whenever an electric current flows through this coil of wire, it acts as a magnet. the strange of it wire coil magnet depends on the size, shape, the number of turns in the coil, and the amount of electric current flowing that the coil. if the coil it self not change in any way; the magnetic strength of the coil will depend on the amount of current through the coil, the stronger the magnetic strength of the wire coil magnets.

If there is no current flow in the coil, it will have no magnetic strength and the coil will turn to a position where there will be no tension on the spring. if you caused a small electric current to flow through the coil, the coil becomes a magnet, and the magnetic force between the wire coil magnet and the horseshoes magnet causes the coil to turn until the magnetic turning force is balanced by the force due to tension in the spring.

When is larger current is made to flow through the coil, the magnet strength of the coil is increased and the wire coil turns further against the spring tension. when you want to find out how to find out the current is flowing in a circuit, all you need to do is to connect the coil into the circuit and measure the angle through which the coil turns away from its possible at rest.

To measure this angle, and to calculate the amount of current which causes the coil to turn through this angle, is very difficult. however, by connecting a pointer to the coil and adding a scale for the pointer to travel across, you can the read about current directly from the scales.