You will need
  • A computer with Internet, a textbook on physics.
Read a physics textbook the basic principle used in electromagnetic instrumentation. As you know, it is based on the interaction of the magnetic field of the permanent magnet with a magnetic field coil wound on a wire frame. Coil winding is placed in a constant magnetic field which is homogeneous to the same. The wire frame is able to rotate around a particular axis. Attached to the coil spring by returning the rotation of the frame and the whole coil in a certain initial position, which is set as zero. Current is supplied to the coil through brushes attached to the axis of rotation of the coil.
Think about it, what happens when the coil electric current flows. In the absence of a current magnetic field, enveloping the coil, it does not interact with it. When the ammeter included in the circuit, the turns of the winding to form a proper magnetic field, which interacts with the magnetic field of an external permanent magnet, causing rotation of the entire frame at an angle. The angle of rotation is determined by the condition of equality of the elastic force of the spring and the force of ampere, the current in the winding from the field. The fact that the rotation of the coil ampere force gradually decreases and the elastic force increases. At some point in time these forces equal in magnitude and of the ammeter stops at a certain value, which you can observe on the scale of the ammeter.
Please note that the voltmeters are working on several types of diagrams, each of which is used in different situations. However, there are classic principles that are used in almost every device that can measure voltage. To measure the voltage at any part of the chain, you need to create the same voltage on the circuit of the voltmeter. However, as we know, a parallel connection circuit of another element the current through this section becomes less, because total current divides into two components, one of which passes through the study area and the other through the connected element. Thus, the connection of the voltmeter distorts the measurement object. This leads to the fact that the resistance of the voltmeter trying to make the most large.
When current flows through the circuit of the voltmeter first, it falls by a certain tension, which you can learn by comparison, and second, the current flowing through the element of the voltmeter, can create a certain effect, say, on any magnetic element. Here are the main ways organizations measure the voltage with a voltmeter.