How does the charge flow in a wire?

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2.1 Charge, time, electricity


The basic quantity of electricity is the electric charge Q. It is measured in coulombs (C). A coulomb is about as much charge as flows through a small incandescent lamp in ten seconds. Every electron and every atomic nucleus has a certain, very small charge. An electron has the charge Q = 1.6 * 10E-19 C (0.00000000000000000016 C). A large number of electrons are therefore always involved in electrical processes.
The electric current is a movement of electric charge. One can therefore ask the question: How much charge Q moves through a wire in a certain time t. When a lot of charge flows in a short period of time, a large current is observed. The current I is therefore defined as follows:

The current I is measured in amperes (A). Smaller currents are measured in milliamps (mA). 1000 mA is equal to 1 A. Much smaller currents are given in microamps (µA). 1000µA = 1 mA.

Current and charge in the circuit (application: battery lamps)

It is usually easier to measure the current than the charge. The charge can be calculated from the current strength and the time by rearranging the above formula. For example, it should be calculated which charge can be moved by a battery cell with the data 1.2V / 500mAh. A current of 0.5A is maintained for one hour, i.e. for 3600 seconds. During this time the load moves:

For the entire charge of 1800C about 10E22 electrons have to be moved (written out in digits: 10000000000000000000000).

YouTube short lecture: charge and amperage