Sensors

When a loop of wire is made to move while in a magnetic field it causes a current to flow in the loop. Off course the loop needs to be continuous otherwise current can not flow.

The strength of this current is dependent on;


This can be seen to be a phenomena similar to the motor action described before only whereas the wire is made to move with the application of an electrical current in this case an application of a movement causes an electrical current; sort of an opposite phenomenon.

There is a major difference however. Let's say a horseshoe magnet is set up as follows and has a piece of wire placed in its magnetic field. (Refer to left hand drawing of fig 20).Let us now say that a voltage is applied such that the wire rotates clockwise and you see a positive current measured on the current meter. If we were to remove the battery and complete the loop as follows (right hand drawing of figure 20) and now physically rotate wire clockwise we would record on the current meter a current that was opposite in polarity to the one needed to make the wire move as in the situation before. This opposite situation has ramifications for our understanding of electromagnetism and we will cover this more fully later on.


We can make up a sensor by having a loop of wire with its two ends as part of the input to a controller. Now if a magnet is caused to move past this coil a voltage will be induced into the wire that could serve to provide a sensory input into the controller. Note that input will only be there as long as the magnet is actually moving. It doesn't matter much which is moving, the coil or the magnet, although for logistical reasons it usual to have the magnet moving. The magnitude of the induced voltage will be dependent on the; Return to introduction