Current in an electrical circuit is the main parameter in which describe a condition of any given point of a chain, and depends on a large number of the factors influencing its size.
It is required to you
- The textbook in physics, the sheet of paper, a pencil, the ampermeter, the voltmeter.
Instruction
1. Remember, using the textbook in physics as current from the law of Ohm is defined. In the ratio this law current is defined as tension relation on the site of a chain to resistance of this site. Thus, change either in tension, or in chain element resistance can be one of the reasons of change of current.
2. And the situation leading to change of any given parameter can be different. For example, if you have the classical divider of tension consisting of two resistive elements, then at change of tension on one of them tension on another immediately will change, so, also current will change. The reason which led to change of tension can consist in change of resistance of one of resistors or in change of the general food of a chain.
3. Pay attention that in practice often currents in chains change because of discrepancy with necessary supply voltage. You can, using the ampermeter, to measure current size in a chain of any device of the house. After that verify this value with stated in the instruction. If you notice discrepancy, then measure tension size in network, you will notice that it is also not equal 220B, as led to change of current.
4. Also pay attention that current in various devices changes at its aging. In this case the mechanism of decrease or instability of current is connected with a number of factors. One of them is deterioration in a condition of contacts that leads to additional voltage drop in a chain on this contact and to decrease in current. Change of the chemical composition of resistive elements and also change of a state between facings of condensers if they are present at this scheme happens other reason, usually.
5. Look at the circuitry of the instrument in which currents to you interest. Practically at each modern device there are transistors. These are three-electrode semiconductor elements. Their feature is that current through any contact depends on tension given on other contact, and the dependence is very strong. As a matter of fact, this property of a semiconductor element is also used at its application, however it leads to undesirable changes in operation of the device. Also It should be noted that at long use of the device containing transistors it strongly heats up. And, as we know, temperature change of semiconductors leads to sharp change of resistance.