One, the construction is different
Static meter is actually has a conductive shell of the electrical detector. The shell of the static meter and the center of the metal rod constitutes a capacitor, they are the two poles of the capacitor. The same as the checker, the pointer (or metal foil) open the size of the number of charged;
For the capacitor, the number of charged is proportional to the potential difference between the two plates, so when they are connected to the two conductors, respectively, by the electrostatic meter pointer of the angle of the judgment of the difference in their potential. Whether the shell is grounded for the display of the potential difference has no effect, but sometimes can increase the stability of the experimental phenomena.
Two, different working principles
Principle of the checker: when the checker indicates that the system is charged, due to the repulsive force of the same kind of charge to make the indicator deflection, it is from the point of view of the force to reflect the situation of the conductor charged. When the indicator system has a certain deflection angle, its gravitational moment and electrostatic moment balance.
The principle of the electrostatic meter is that the electrostatic meter itself is a capacitor with a small capacitance. The metal ball, metal rod and pointer are equivalent to an electrode of the capacitor, and the metal case is also equivalent to an electrode, and they are insulated from each other.
The size of its capacitance is determined by the size of the geometry of the metal shell and the length and position of the metal rod and pointer. Because the deflection angle of the pointer changes on the capacitance of the electrostatic meter is very small, so in the pointer rotation process can be approximated that the capacitance of the electrostatic meter value is unchanged.
Three, the use of different
The main purpose of the checker: to test whether the object is electrically charged, compared with the type of charge and the amount of charge, etc..
The use of electrostatic meter:? Because of the special structure of the electrostatic meter, it has some of the role of the checker can not be replaced. It can not only qualitatively measure the potential difference between the two conductors (this point has been above, so do not repeat), but also qualitatively measure the potential of a conductor, and can even measure the potential difference in the DC circuit.
The scale on the electrostatic meter is generally static volts (electrostatic system unit) for the unit, and 1 static volts = 300 V. Therefore, the general DC voltage can not make the electrostatic meter pointer has a significant deflection. If the static meter connected to the DC circuit with hundreds, thousands or even tens of thousands of volts, the static meter pointer will have a significant deflection, you can also use the static meter to measure the voltage between two points.
For example, the electrostatic meter connected to the secondary coil of the induction loop, the pointer deflection angle will be large and small, indicating that the output of the induction loop is unstable pulsating voltage.
Expanded
One, the static meter can not replace the voltmeter to measure the potential difference between the two points of the DC circuit:
If the static meter of the metal ball and the grounding knob were connected to the circuit of the two points, the static meter will be charging, theoretically speaking, can be qualitatively reacted to the size of the voltage through the pointer angle situation, but due to in the general DC circuit in the voltage between the two points is relatively small, the electrostatic meter electrode charge is very small, resulting in almost no deflection of the pointer.
Two, the voltmeter can not replace the electrostatic meter to measure the potential difference between the two plates of the capacitor:
Structurally speaking, the voltmeter is different from the electrostatic meter, it is a magneto-electric ammeter with a large voltage divider resistor in series modified into the current flowing through the ammeter indirectly react to the magnitude of the voltage in the DC circuit between the two points.
When measuring the potential difference between two charged bodies with an electrostatic meter, because of its own capacitance is very small, the effect on the original capacitor's charged situation is negligible.
But if the voltmeter to measure the potential difference between the two plates of the capacitor, the voltmeter and the capacitor constitutes an RC circuit, resulting in the discharge of the capacitor, the charged situation has changed. So in the investigation of parallel plate capacitor capacitance and which factors related to the experiment, can not use the voltmeter instead of static meter.
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