All electric devices are calculated on a certain tension, and all power supplies are constructed so that tension developed by them did not go beyond certain limits.
Instruction
1. To explain, than tension differs at most current, resistance and power, it is possible to use such analogy. Imagine a pipe to which a certain pressure of gas or liquid is attached. This pressure - tension analog. The amount of the substance passing through a pipe per unit of time will depend on pressure and the section of a pipe. Here pipe section - resistance analog, and amount of the substance passing through a pipe per unit of time - a current analog. At the same time, on a pipe it will be allocated in the form of a certain power because of friction is warm. It is an analog of the thermal power which is allocated on the conductor with current.
2. Tension is measured in volts. This unit of measure is called in honor of the Italian scientist Alessandro Volt, the inventor of one of types of electrochemical sources of current. Thousand volts are called kilovolt, one million volts - kilovolt. The thousand share of volt carries the name of millivolt, million - microvolt.
3. Tension happens to constants and variables. In the second case it periodically changes polarity with a certain frequency. Alternating voltage has two values: amplitude and acting. The first characterizes fluctuation band, and the second - the equivalent constant tension which would allocate the same power on the same loading. The ratio between the amplitude and operating values of tension depends on its form. At sinusoidal single-phase tension the amplitude value exceeds acting in the number of times equal to a root from two.
4. Concept "dangerous tension" not absolutely true. The danger of impact of electricity on the person depends not on tension, and at most current. Another thing is that skin has a certain resistance and therefore dangerous current in it can arise at a certain value of tension. Skin of different people has various resistance, also it depends on a mental and physical state. Therefore the threshold of dangerous tension can change even at the same person. At a certain tension skin makes the way, and the smaller resistance of hypodermics is attached to a source considerably, what is even more dangerous.
5. Besides electric there is also mechanical tension. It arises in designs to which external mechanical influences are attached. Besides, in some designs there can be at a fabrication stage internal tension. If to make an object of transparent material and to place between two polarizers, it is possible to define presence in them of such tension. And figuratively tension call tension of mentality of the person.