Electric charge is the size characterizing ability of a physical body to be a source of the electromagnetic field and to take part in interaction with other similar sources. Still ancient Greeks found out that if to rub a piece of amber about wool, then it will gain ability to attract easy objects. Amber in Ancient Greek language was called "electron".
Instruction
1. The simplest device – the electrometer is for certain familiar to the school students studying physics in high school. It consists of a metal core with the round horizontally located ledge. The arrow which can freely rotate is got on this ledge. What will occur if the charged body touches a metal core of the electrometer? A part of a charge kind of will flow on a core and an arrow. But as these charges of the same name, they will push away each other. And the arrow will deviate initial situation on some corner. By means of the graduated scale it is measured and count charge size. It is easily possible to understand that the more the charge, the more will be a corner of a deviation of an arrow of the electrometer and vice versa. Certainly, by means of such primitive device it is possible to make only approximate determination of size of a charge. If high precision is necessary, sensitive electronic electrometers are used.
2. You can use Coulomb's law: F = kq1q2/r^2 where F is force of interaction between two charged bodies, q1 and q2 – the size of their charges, r – distance of these bodies, and k between centers – proportionality coefficient. In other words, if you have a body which charge q1 is known to you, then, having brought the second body which charge of q2 needs to be determined on distance of r and force of interaction of F by the sensitive device dynamometer, you easily calculate a required charge of q2 on a formula: q2 = Fr^2 / (kq1).
3. It is also possible to clean charge size, having measured current in a chain. The fact is that the total size of the charge which leaked through the cross section of any conductor is calculated on a formula: Q = IT, where I – current in amperes, and T – time in seconds. For this experience you need a stop watch and the ampermeter – the device for determination of current. Collect an electrical circuit where the ampermeter is switched on, include current, write down the indication of the ampermeter. Open a chain, having at the same time switched off a stop watch. Write down, what is the time current was in a chain. And on the above-stated formula count total electric charge.