Magnetic field represents one of types of matter which can make power impact on other fields or some types of substance. It means that magnetic the field has energy by means of which performs work, influencing bodies. This energy can be calculated, knowing characteristics of magnetic field.

## It is required to you

- - tester;
- - source of an alternating and direct current;
- - calculator.

## Instruction

1. Calculate energy of magnetic field which is formed in the coil with current. For this purpose connect it to a DC power source and by means of a tester measure its force in amperes. Define inductance of the coil. It depends on its geometrical sizes and magnetic properties of substance which is in it. To achieve the greatest indicators of inductance, take coils with iron cores. The inductance of the coil in Gn, as a rule, is specified on it.

2. If the inductance of the coil is unknown, measure it independently. For this purpose attach it to a source of alternating current with the known frequency. By means of a tester measure tension and current in the coil. Define value of inductance of L, having divided value of tension of U into number 6.28, frequency of alternating current of f and current: I, L=U / (6.28•f•I). Receive value of inductance in Henry.

3. After change of inductance of the coil and current in it calculate value of energy of magnetic field. For this purpose increase inductance of L by the current I squared. Divide result into number 2:. Result receive W=L·I \in Joules.

4. For example, if on the coil inductance 3 mgn current 4 A proceeds, then energy of magnetic field in it is calculated by W=L·I \formula · 10^(-3) • 4^(2)/2=24^(-3)=24 mdzh. Previously transfer value of inductance from mgn to Gn.

5. Calculate energy of magnetic field on a magnetic flux which is formed by the current proceeding on the inductance coil. For this purpose F in webers increase value of a magnetic flux by the current which is measured in coil I connected to a DC power source by means of a tester, and divide result into number 2: W=F·I/2. The result will be received in Joules. For example, at a magnetic flux of 0.5 Wb and current 6 A energy of magnetic field will be equal in the coil to J W=0.5•6/2=1.5.