Voltage and current are brothers, current flows from a place where the voltage (level) is high to a place where the voltage (OVK Malmö) is low, a current must be generated because of the presence of a voltage, but the presence of a voltage does not necessarily generate a current – if there is only a voltage and no current, it can be proved that there is an interruption in the circuit (e.g., there is a switch in the circuit).
If there is only voltage but no current, it is evidence of a circuit break (e.g. a switch in the circuit). In addition, sometimes the measurement of voltage is normal but the measurement of current is not necessarily normal, such as a slight short-circuit phenomenon or a component of the resistance value of the phenomenon of large, etc., so in the maintenance must be combined with the voltage value and current value to analyze. When testing the unknown voltage or current with the multimeter, be sure to set the gear into the highest grade, such as measuring the value and then gradually lower the gear.
II.Resistors
Various materials present a certain resistance to the current that passes through them, and this resistance is called resistance, and the entity (element) that has this physical property of aggregate resistance is called a resistor (simply a conductor with a resistance value). Its role in the circuit is very important, in the computer boards and peripherals in the number is also very large.
Its classification is also varied, if classified by use: current limiting resistors, buck resistors, voltage divider resistors, protection resistors, start-up resistors, sampling resistors, decoupling resistors, signal attenuation resistors, etc.; if classified by shape and production materials: gold film resistors, carbon film resistors, cement resistors, non-inductive resistors, thermistors, varistors, pull-wire resistors, chip resistors, etc.; if categorized by power: 1/ 16W, 1/8W, 1/4W, 1/2W, 1W…… and so on.
These resistors are common resistors, so their resistance value of the nominal method we must know, the following I will take the computer host card on the most common chip resistors as an example (the other resistors nominal method of the same): Chip resistor nominal method of digital and color ring method of these two.
First of all, the digital method, usually there are three resistors on the number XXX, the first two numbers in turn is the number of tens and digits, the last number is 10 of the Xth power, the specific resistance value of the resistor is the first two numbers of the two-digit number multiplied by 10 of the Xth power of the ohms, such as labeled with a 104 resistor resistance is 100000 ohms (i.e., 100KΩ), labeled with a 473 resistor resistance value is 47000 ohms (i.e., 47KΩ); the following author to say a few words about the color ring method, this nominal method is the most common in all the resistor nominal method (patch shape of the relatively few), the common color ring usually has four rings, we will be the gold or silver ring as the last ring, the first three rings of the color corresponds to the corresponding number, we know the number of numbers we need to use the number of the above mentioned method of reading the value of its resistance.