Experimental part. The laboratory plant is shown in fig

The laboratory plant is shown in fig. 13.1. The audio-signal generator is a source of an alternating current which flows in coil A connected to the generator. This coil (a circular current) creates a varying magnetic field. The induction sensor B is also a small coil coaxial with coil A. The current induced in coil B by the variable magnetic field is measured by the milliammeter. Value of the milliammeter current is proportional to amplitude of magnetic field intensity. Shifting the sensor along scale S, change of milliammeter current reflects a change in magnetic intensity.

 

1. Check electrical connections. Set up 0.15 mA milliammeter range.

2. Switch on the generator. Set up frequency of generator’s signal to be 10 kHz and maximum output voltage.

3. Place the indication coil B in the center of the circular current (l = 0). Make sure that pointer of the milliammeter is within the scale.

4. Varying position l of the indicating coil B from 0 with step of 2 scale graduations (2 cm, if using a scale rule), fix value of the milliammeter current H. Stop measurements when a change in current value becomes undetectable. Write down obtained results into table 13.1.

5. Using experimental data, examine theoretical dependence Н = f (l) by the linearization method.

This method implies a choice of new variables (a function and an argument) in relationship (13.6) in order to obtain a linear dependence between these variables. Such dependence can be easily verified since its plot is a straight line.

It is not difficult to demonstrate that making change

 

, (13.7)

 

in formula (13.6), relation gets the needed form

 

, (13.8)

 

where , . Calculate y and x using data obtained in experiment and show graphically dependence between them. On account of the form of dependence , make a conclusion about results of the examination of relationship (13.6).

 

 

Table 13.1

	Н	x	y