3.8.4 Experimental procedures
1)Describe the electrostatic field distribution of coaxial cable
(1)Based on the simulation model shown in Figure 3.8.2(a),the inner and outer electrodes of the conductive microcrystalline(if the water tank type electrostatic field plotter is used,the inner and outer electrodes in the water tank)are respectively connected with the positive and the negative poles of the DC regulated power supply.
(2)The positive and negative poles of the voltmeter are respectively connected with the synchronous probe and the negative pole of the power supply,and the synchronous probe is moved to measure the equipotential line cluster of the coaxial cable.The potential difference between two adjacent equipotential lines is 1 V.
(3)The concentric circle cluster of equipotential lines is drawn by taking the average distance from each point on each equipotential line to the origin as the radius r(U0=10 V,and the equipotential line is drawn by taking the voltage U=1 V,2 V,3 V,4 V,5 V and 6 V).Then the electric field line is drawn according to the principle of electric field line and equipotential line orthogonality,and the direction of electric field intensity is pointed out,and a complete electric field distribution map is obtained.
(4)On the coordinate paper,the relation curve of the relative potential Ur/U0 and ln r is drawn.According to the nature of the curve,it is shown that the equipotential line is a concentric circle with the center of the inner electrode as the center of the circle.
2)Describe the electrostatic distribution formed by a wedge electrode and a strip electrode
(1)The experimental plate composed of a wedge electrode and a strip electrode is shown in Figure 3.8.4.Connect the circuit according to the experimental requirements,and adjust the voltage between the two electrodes to 10 V,and lay the recording paper on the upper plate.
(2)Starting from 1 V,move the synchronous probe,use the probe above the conductive microcrystalline to find the isopotential point,and then click the probe above the recording paper to measure a series of isopotential points.(https://www.daowen.com)
(3)It is required to measure 9 isopotential lines,and find more than 10 points on each isopotential line,and then find more isopotential points near the end of the electrode.The equipotential line is drawn according to the equipotential point,and then the electric field line is made.
(4)When making the electric field line,it should be noted that the electric field line is orthogonal to the equipotential line.The conductor surface is an equipotential surface.The electric field line is perpendicular to the conductor surface.
(5)The electric field line originates from the positive charge and stops at the negative charge.The density degree indicates the strength of the electric field,and the direction of the electric field line is drawn according to the positive and negative electrodes.
Figure 3.8.4 Structure diagram of wedge and strip electrode test plate
1—wedge electrode;2—strip electrode
3)Tips and attentions
As the current at the edge of conductive microcrystalline can only flow along the edge,the equipotential line must be perpendicular to the edge,causing serious distortion of the equipotential line and electric field line.This is due to the“edge effect”when using a finite simulation model to simulate infinite space electric field.In order to reduce the influence of this effect,we should use“infinite”conductive microcrystals to conduct experiments,or artificially cut the edge of conductive microcrystals into the shape of electric field lines.
