resistance? Software engineers still know, after all junior high school physics, I have learned, it is the kind of sliding rheostat. However, the general impression of the software engineers resistance will stop here.
Sliding rheostat, it is an ancient and deeply into the minds of each of us deep in electronics, many people initially interested in E is from its beginning. Glide, the lamp gradually brightening; slip past, the lamp gradually darker. This is the teacher said variable resistance.
In our actual hardware life, variable resistor, there are many, but not so big, so big push to the head there is no way the board ah. The variable resistor can be placed on the circuit board are relatively small, even now there patch variable resistor, the smaller heads.
In fact the most used or fixed value resistor, usually at the design stage, because to find the best resistance, so use a variable resistor, after the design is completed, who would not be right of resistance to slide to slide, Therefore, it will be replaced with a fixed resistor.
Many people see the resistance of the fixed resistor basically had a few, what 1k, 1.5k, 2k, etc., will not be what 1.21k, if so, then how much ah come up with a fixed value, the factory would not do such a stupid thing. In fact fixed resistors, resistor on almost an order of magnitude does not cause much difference, even if very strict design requirements of resistance, or you can use to string together multiple resistance and, in general, currently on the market to buy the resistance is probably more than 1,000, most of us have been designed to meet the needs, so do not worry.
And then went on to say resistance, as classroom teacher in high school told us, the resistance is to block current flow, the heat energy into it. So, feel the resistance, will feel a little more or less heat. Some people say, this is not a waste of energy? In fact, for well-designed hardware systems, such losses (power) it is very small, even negligible, so do not worry.
There is pressure resistance values and power values, not just use, low-power resistive heads are generally small, powerful head was relatively large, such as high-power resistor can be directly connected to the 220v AC, a small power resistor connected to burned. The reason is the low-power carbon film resistors are generally, unable to bear the heat, if the current is too large, too much heat, the temperature is too high, it is burnt. You can understand the resistance to drainage canal from the river to a bar and then drained into a small brook scene, the river flow is very large, so to add a canal, so that the river water into the canal, then the flow becomes small again the introduction of canal water rivers flow even smaller. Think again, a dam is not only very wide and very strong, which is equivalent to high-power resistance, resistance big points; canal dam was not so wide, so the equivalent resistance in power; the more narrow dam , the equivalent resistance of small power. Not very appropriate analogy, is that a meaning.
We usually use small power resistors are 1 / 8w,, there are 1 / 2w, 1w, relatively large power of 1 / 4w in power 2w has to be chosen according to the actual needs of the circuit. Prices are high power resistors, power resistors with a small place that would use small power resistors, no need to go to waste.
Resistance is the most basic hardware elements, software engineer to know not only the variable resistor, a fixed resistor also know, to understand the power of resistance.
According to different materials, divided carbon film resistors, metal film resistors, wire wound resistors, cement resistance, etc., carbon film resistors less power, large power resistance cement, but the head is not small.
According to mounting points, there are chip resistors and resistor line, the so-called chip resistors, is only two joints, no leads at both ends, so it saves installation space, now used in the actual product placement is very common.
Many resistance effect, not only step-down, split, can do load, like a filter and impedance matching. When just getting started, just you need to know shunt, blood pressure, current limiting.
Knowledge of the area is still a lot of resistance, we are now on the first point, later in the actual application to add. Thank you for reading.
