How to count a charge

How to count a charge

It is possible to define a charge in case to bring it in electric field with the known tension and to measure force which on it will work. It is possible to find a charge, having measured its force of interaction with the known charge. And the charge which passed on the conductor for some time can be found through value of current.

It is required to you

  • - sensitive dynamometer;
  • - electroscope;
  • - stop watch;
  • - tester.


1. Bring a charge in electric field and the known tension. If tension in this point is unknown, measure it by means of the known charge or the electroscope. On the brought unknown charge from the field the Coulomb force which measure by means of a sensitive dynamometer will work. Count q charge size, having divided force operating from field F measured in Newtons, into his tension E measured in volts on meter or Newtons on a q=F/E Pendant. Receive result in Pendants.

2. If the unknown charge interacts with the known charge, by means of a dynamometer measure force of their interaction. Consider that heteronymic charges are attracted, and of the same name make a start. For this purpose take a sensitive tortional dynamometer better. Measure distance between charges which interact. Measure force in Newtons, and distance in meters. To count an unknown charge of q, increase the measured force of F by a distance square between r charges. Divide the received number into the size of the known charge q0 and coefficient of k=9∙10^9 (q=F∙r² / (q∙k)). The result will turn out in Pendants.

3. Current is called the ordered movement of charges in the conductor. Therefore through the cross section of the conductor in a definite time there passes a number of a charge. To find it, determine current, having attached the tester switched to the ampermeter mode in an electrical circuit. Measure current in it in amperes. If tension on the conductor and its resistance, then current of I is known, calculate, applying Ohm's law for subcircuit, having divided U tension into resistance of R (I=U/R). Define time which the charge proceeded on the conductor by means of a stop watch. Count the size of a charge of q passing during t through the cross section of the conductor, at the current of I, having multiplied these sizes (q=I∙t).

Author: «MirrorInfo» Dream Team