How to find electric charge

How to find electric charge

It is possible to find value of electric charge in two ways. The first – to measure force of interaction of an unknown charge with known and by means of Coulomb's law to calculate its value. The second – to bring a charge in the known electric field and to measure force with which it affects it. For measurement of a charge of the conductor proceeding through cross section in a definite time measure current and increase it by value of time.

It is required to you

  • sensitive dynamometer, stop watch, ampermeter, measuring instrument of electrostatic field, air condenser.


1. Measurement of a charge in its interaction with known zaryadomesl the charge of one body is known, bring to it an unknown charge and measure distance between them in meters. Charges will begin to interact. By means of a dynamometer measure force of their interaction. Calculate value of an unknown charge - for this purpose increase a square of the measured distance by value of force and divide into the known charge. Divide the received result into number 9 • 10^9. The value of a charge in Pendants will be result (q=F • r² / (q0·9 · 10^9)). If charges make a start, then they of the same name if are attracted – heteronymic.

2. Measurement of value of the charge brought in electric to a poleizmerta value of constant electric field by the special device (measuring instrument of electric field). If there is no such device, take the air condenser, load it, measure tension on its facings and divide not distance between plates - it is and there will be a value of electric field in the condenser in volts on meter. Bring an unknown charge in the field. By means of a sensitive dynamometer measure force which affects it. You take measurement in newtons. Divide value of force into electric field strength. The value of a charge in Pendants (q=F/E) will be result.

3. Measurement of the charge proceeding through cross section you provodnikasoberit an electrical circuit with conductors and consistently connect to it the ampermeter. Close it on a source of current and measure current by means of the ampermeter in amperes. At the same time a stop watch note time during which in a chain there was electric current. Having increased value of current by the received time, learn the charge which passed through the cross section of each conductor during this time (q=I•t). At measurements you watch that conductors did not overheat and there was no short circuit.

Author: «MirrorInfo» Dream Team