Unit 11. Electrical Current

Date: 2015-10-07; view: 394.

Serve as a simultaneous interpreter of the summary stated above.

Make a summary in Russian of the text you haven't read.

Current in general is the flow of any material, like water, from one point to another. Assume there are two containers connected together with a channel and they are filled with water. When one container is higher than the other one, the water in it will have a higher potential energy. Therefore the potential energy of the water turns into the kinetic energy through the open channel, as shown in the figure below:

The intensity of the current is simply known as the volume of the flowing material in time, the more material flows in a amount of specific time, the more is the current intensity. These also apply to the electrical current. The electrical current is made of electrons flowing in a closed circuit from a point with a higher electrical potential (voltage) to the other. The volume of electrons is measured by their electrical charge. Therefore we can rephrase the definition, saying that the electrical current is made of electrical charges flowing in a closed circuit.

The value of current or the current intensity is equal to the volume of the flowing electrical charge in the unit of time, second, as shown in the formula below:

were I is the electrical current, which we refer to as Current, q is the positive electrical charge in Coulomb (the electrical charge unit) passing in the time t with the unit of seconds. If any two of the parameters are known, the other one can be calculated using the formula above.

The direction of current is assigned to the flow of positive charges in the circuit. But the only flowing particles are electrons that generate current having a negative charge. You may wonder why scientists use the flow of the positive electrical charges while they are not moving at all! It's quite simple: years ago when scientists were developing formulas for their experiments, they didn't know about the electrons. They only knew about charges and therefore they randomly assigned the current flow direction to the positive charges. Afterwards when they knew about electrons, it didn't really matter in the final results which direction they used. Because they only required to change the parameter sign in every formula. Therefore to be compatible with the previous formulas, which were already settled in the scientific world, they didn't change the direction. You can simply assume that when the negative charge is flowing in one direction, the positive charge is virtually flowing in the reverse direction.