Introduction to the electrical electricity and phenomena
2º international System and change of units.
Each PU, for example the Kilo when we spoke of weight, has a series of multiples and sub-multiple to refer to weights majors or minors to us, for example, if we are in a laboratory, we cannot say that this tablet or on contains 0.005 of paracetamol. But normal and the comfortable thing is to speak of 5 milligrams of paracetamol, because the previous thing, among other things, can take to errors. We will see a table where is the change of a unit, between multiples (but great) and sub-multiple (but small) In our case, each step is going to be thousand times greater (or minor).
There are other multiples majors, as the Tera (case of the Terabyte) and smaller others as femto.
3. Exponential numbers
In the technology very great numbers are handled and very small and, for this reason, we have seen before the table of multiples and sub-multiple, but when we must work with operations, but the practitioner is to use the exponential numbers.
3.1 What is. It is an annotation of two numbers. The one down is called base and the one of above, exponent and have 5 form ³, where 5 are the base and 3 the exponent
3.2 What represents. The answer would be a compressed number, so that a number without as much number can be shelp, for example, the previous case, 5 ³, as 5 are high to 3, to obtain the number, we would have to multiply 5 so many times as it says the exponent, that is 5*5*5 = 125.
Any lifted base to 0 is worth 1, for example 250 = 1
We will see because this ahead but
3,3 Cuidadin with the signs negatin. Then that, taken care of with the negatives that according to where they are a thing is worth different from another one. For example, -34 is not the same a (- 3) 4. In the first case, we have:
-34 = – (3 • 3 • 3 • 3) = -81
and in the second (- 3) 4 = -3 • -3 • -3 • -3 = 81.
In this case, the result has been different. What would happen if we changed the exponent to an odd number.
We will see now: -35 = – (3 • 3 • 3 • 3• 3) = -243
(- 3) 5 = -3 • -3 • -3 • -3 • -3 = -243
In this case they have agreed! This is due to that uneven by odd number he is even, but even * uneven is uneven. We remembered?
Resistivity is called to the specific opposition that has each material to be against to the passage of an electrical current. Ρ imagines by the Greek letter and it is moderate in [Ω·mm ² /m].
Each material, independent of its dimensions, has a unique resistivity, but it can raise or lower when modifying the room temperature.
A cable with some concrete dimensions, is going to have a total resistance that comes by the expression:
l = Length of the cable
A = Cross-sectional Area
ρ = resistivity
To calculate the resistance of a rectangular bar of side 2 * 3 cm and length 4 km if 0.0020 resistivity is Ω*mm2/m
First it is to calculate the surface of the bar that comes dice by base X height, therefore:
S = 2 * 3 cm ² = 6 cm ² = 600 mm ²
Now, we passed 4km to meters, that give 4000 meters us
To pass 25000 mA to KA
Beam just like in section 6, but in this case, the result of the operation is 1, and thus to demonstrate 2º postulated (the one that says us that any number lifted to zero is 1)
To calculate the electrical charge, if through a circuit passes an intensity of 23 mA in a time of 4 s.
To mount the circuit of the book with the program crocodile and to answer the questions. To raise DRIVE a pdf with the circuit (screenshot) and the answers.
The relay is an electromechanical device composed of a winding that, to the fed being, moves a system of mechanical elements that bring about the commutation of the electrical terminals. Very they are used in the automobile to handle high currents (current of lights, to activate motor starts, etc when activating the controls that we have in steering wheel, key contact, etc, that they handle small currents. For example, when activating the ignition key, takes place a commutation in a small commutator of the bowler, that the winding feeds on a relay and this it causes that the terminals of the same are closed to feed a starter engine that needs great amperage.
We will see an explanatory video
3º Hacer just like in exercise 2, using a relay, with double contacts.