20160225 One question per day
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20160225 Daily Question: How to distinguish between resistors, capacitors, and inductors, and how to calculate them?
1. Color: Resistors usually come in two colors. Beige is typically the color of 4-ring resistors, while blue is used for high-precision 5-ring resistors. Inductors are usually the two green types shown in the diagram. As for capacitors, I don’t see them very often; those I have seen are white-green in color, which is lighter than that of inductors. Diodes need not be discussed here; only voltage-regulating diodes are used, which come in glass-and-paint enclosures. Typically, they have two color bands indicating the voltage regulation value. 2. Shape: The resistance is like a bone chewed by a dog – clearly thicker at the two ends and thinner in the middle, with a uniform shape. Where it should connect to the lead, it suddenly isn’t there. Inductors are different; compared to resistors, they are much thicker, almost as thick as each other. The area where they connect to the leads tapers gradually, and they don’t become as thin as resistors do. Capacitance is similar to resistance; it is determined by the physical structure. 3. Measurement: There’s no need to talk about resistance measurement – everyone knows how to do it. Except for special types of resistors, their values are usually in the range of a few hundred, a few thousand, or even higher. Inductors are different; when measured, their resistance is generally below 10 ohms. Capacitance cannot have its resistance value measured. 4. Circuit: Observe the way these components are connected in the circuit. If it is an output or input point, inductors are generally connected in series; resistors and capacitors can also be identified preliminarily based on their relationships within the circuit. The results are mainly measured using a multimeter. If inductors and capacitors are read using the color codes mentioned above, the measurement results will be quite different. If it is a resistor, it won’t be confused with an inductor, because when a resistor fails, it’s basically always due to an open circuit. As for distinguishing between resistors and capacitors, in addition to checking the color rings and comparing the measurement results, for resistors that are open-circuited or capacitors with leakage, one can only rely on the symbols on the circuit board or by removing the coating to see them. Due to manufacturing processes, after the paint is removed, spiral patterns connect the two electrodes. The capacitor, on the other hand, is a layer of copper without spirals, and it does not connect the two electrodes. It’s clear from the diagram above. On the left is the resistor, and on the right is the capacitor.
On a circuit board, resistance is denoted by R, capacitance by C, and inductance by L. 1. A capacitor is an electronic component that stores and releases charge. The basic working principle of a capacitor is charging and discharging; of course, it also has functions such as rectification, oscillation, and others. Furthermore, the structure of a capacitor is very simple; it consists mainly of two positive and negative electrodes along with an insulating material placed in between them. Therefore, the type of capacitor is primarily determined by the electrodes and the insulating material. In the circuits of computer system motherboards, expansion cards, and power supplies, several types of capacitors are used, including electrolytic capacitors, paper capacitors, and ceramic capacitors, with electrolytic capacitors being the most common. Inductance: Have you seen transformers? The coils made of wires on them are a type of inductance. In simple terms, inductance refers to a coil; when a varying current passes through it, it produces effects that are different from those of ordinary wires, which is why it’s given this name. Inductance only works with non-constant currents. Its characteristic is that the voltage across it is proportional to the rate of change of the current passing through it (i.e., its derivative), and the proportionality constant is known as its “self-inductance”. The reason inductance works is that it generates a changing magnetic field when a non-constant current flows through it, and this magnetic field in turn affects the current. Therefore, any conductor that has a non-constant current flowing through it will generate a changing magnetic field, which will affect the current, meaning that every conductor exhibits self-inductance.
2. Capacitance in series and parallel: C (capacitance) = Q (total charge) / U (voltage). Inductance in series and parallel: L = L1 * L2 / (L1 + L2).
3. Capacitive reactance = 1/2 * π * f * C (where C is capacitance). Inductive reactance = 2 * π * f * L (where L is the self-inductance coefficient). In a circuit, current flows sequentially through each component. The basic characteristic of a series circuit is that there is only one path for the current to flow. From this, we can conclude that series circuits have the following five characteristics: (1) The current flowing through each resistor is equal. Because in a DC circuit, the current intensity is the same across all cross-sections of the same branch. (2) The total voltage (the voltage across a series circuit) is equal to the sum of the individual voltages (the voltage across each resistor), that is, U = U1 + U2 + … + Un. This can be directly derived from the definition of voltage. (3) The total resistance is equal to the sum of the individual resistances. Applying Ohm’s law to each resistor gives U1=IR1, U2=IR2, …, Un=IRn. Substituting these into U=U1+U2+……+Un and noting that the current through each resistor is equal, we obtain U=I(R1+R2+Rn). This formula shows that if a resistive element with a resistance value of R = R1 + R2 + … + Rn is used to replace the original series circuit of n resistors, the current through this element will be the same as the current in the original series circuit. Therefore, the resistance R is called the equivalent resistance (or total resistance) of the original series resistance. Therefore, the total resistance is equal to the sum of the individual resistances. (4) The voltage across each resistor is proportional to its resistance value, because Ui = IRi. (5) The power allocated to each resistor is proportional to its resistance value, since Pi = I2Ri. Characteristics of series connection: The switch controls the entire circuit regardless of its position; in other words, its function is independent of where it is located. There is only one path for electric current to take, and the current that passes through one light bulb must also pass through the other one. If one light is turned off, the other light must also be turned off. Advantages of series connection: In a circuit, if it is necessary to control all components, a series circuit can be used for that purpose ； Disadvantage of series connection: as long as one link is broken, the entire circuit becomes open. That is, the electronic components connected in series cannot function properly. 4. Direct current: A current whose magnitude and direction do not change over time. Also known as constant current. The circuit that is thus formed is called a direct current circuit; it is a closed conductive loop composed of a direct current power source and resistors. In this circuit, a constant electric field is established. Outside the power source, positive charges flow from areas of higher potential to areas of lower potential through resistors; inside the power source, non-electrostatic forces exerted by the power source overcome the electrostatic forces, allowing the charges to move from areas of lower potential to areas of higher potential. This cycle repeats, forming a closed current path. Therefore, in a DC circuit, the role of the power source is to provide a constant electromotive force that does not change over time, thereby supplying the energy needed to generate the Joule heat dissipated in the resistors. Alternating current: An electric current whose direction and intensity (magnitude) change periodically. When the coil rotates at a constant speed in a magnetic field, an alternating current is generated within the coil, whose magnitude and direction change periodically. The alternating current in use today generally changes direction and intensity 50 times per second. The electricity used in common items such as light bulbs and electric motors is alternating current. In practice, alternating current is represented by the symbol “~”
2. Capacitance in series and parallel: C (capacitance) = Q (total charge) / U (voltage). Inductance in series and parallel: L = L1 * L2 / (L1 + L2).
3. Capacitive reactance = 1/2 * π * f * C (where C is capacitance). Inductive reactance = 2 * π * f * L (where L is the self-inductance coefficient). In a circuit, current flows sequentially through each component. The basic characteristic of a series circuit is that there is only one path for the current to flow. From this, we can conclude that series circuits have the following five characteristics: (1) The current flowing through each resistor is equal. Because in a DC circuit, the current intensity is the same across all cross-sections of the same branch. (2) The total voltage (the voltage across a series circuit) is equal to the sum of the individual voltages (the voltage across each resistor), that is, U = U1 + U2 + … + Un. This can be directly derived from the definition of voltage. (3) The total resistance is equal to the sum of the individual resistances. Applying Ohm’s law to each resistor gives U1=IR1, U2=IR2, …, Un=IRn. Substituting these into U=U1+U2+……+Un and noting that the current through each resistor is equal, we obtain U=I(R1+R2+Rn). This formula shows that if a resistive element with a resistance value of R = R1 + R2 + … + Rn is used to replace the original series circuit of n resistors, the current through this element will be the same as the current in the original series circuit. Therefore, the resistance R is called the equivalent resistance (or total resistance) of the original series resistance. Therefore, the total resistance is equal to the sum of the individual resistances. (4) The voltage across each resistor is proportional to its resistance value, because Ui = IRi. (5) The power allocated to each resistor is proportional to its resistance value, since Pi = I2Ri. Characteristics of series connection: The switch controls the entire circuit regardless of its position; in other words, its function is independent of where it is located. There is only one path for electric current to take, and the current that passes through one light bulb must also pass through the other one. If one light is turned off, the other light must also be turned off. Advantages of series connection: In a circuit, if it is necessary to control all components, a series circuit can be used for that purpose ； Disadvantage of series connection: as long as one link is broken, the entire circuit becomes open. That is, the electronic components connected in series cannot function properly. 4. Direct current: A current whose magnitude and direction do not change over time. Also known as constant current. The circuit that is thus formed is called a direct current circuit; it is a closed conductive loop composed of a direct current power source and resistors. In this circuit, a constant electric field is established. Outside the power source, positive charges flow from areas of higher potential to areas of lower potential through resistors; inside the power source, non-electrostatic forces exerted by the power source overcome the electrostatic forces, allowing the charges to move from areas of lower potential to areas of higher potential. This cycle repeats, forming a closed current path. Therefore, in a DC circuit, the role of the power source is to provide a constant electromotive force that does not change over time, thereby supplying the energy needed to generate the Joule heat dissipated in the resistors. Alternating current: An electric current whose direction and intensity (magnitude) change periodically. When the coil rotates at a constant speed in a magnetic field, an alternating current is generated within the coil, whose magnitude and direction change periodically. The alternating current in use today generally changes direction and intensity 50 times per second. The electricity used in common items such as light bulbs and electric motors is alternating current. In practice, alternating current is represented by the symbol “~”
On a circuit board, resistance is denoted by R, capacitance by C, and inductance by L. 1. A capacitor is an electronic component that stores and releases charge. The basic working principle of a capacitor is charging and discharging; of course, it also has functions such as rectification, oscillation, and others. Furthermore, the structure of a capacitor is very simple; it consists mainly of two positive and negative electrodes along with an insulating material placed in between them. Therefore, the type of capacitor is primarily determined by the electrodes and the insulating material. In the circuits of computer system motherboards, expansion cards, and power supplies, several types of capacitors are used, including electrolytic capacitors, paper capacitors, and ceramic capacitors, with electrolytic capacitors being the most common. Inductance: Have you seen transformers? The coils made of wires on them are a type of inductance. In simple terms, inductance refers to a coil; when a varying current passes through it, it produces effects that are different from those of ordinary wires, which is why it’s given this name. Inductance only works with non-constant currents. Its characteristic is that the voltage across it is proportional to the rate of change of the current passing through it (i.e., its derivative), and the proportionality constant is known as its “self-inductance”. The reason inductance works is that it generates a changing magnetic field when a non-constant current flows through it, and this magnetic field in turn affects the current. Therefore, any conductor that has a non-constant current flowing through it will generate a changing magnetic field, which will affect the current, meaning that every conductor exhibits self-inductance.
2. Capacitance in series and parallel: C (capacitance) = Q (total charge) / U (voltage). Inductance in series and parallel: L = L1 * L2 / (L1 + L2).
3. Capacitive reactance = 1/2 * π * f * C (where C is capacitance). Inductive reactance = 2 * π * f * L (where L is the self-inductance coefficient). In a circuit, current flows sequentially through each component. The basic characteristic of a series circuit is that there is only one path for the current to flow. From this, we can conclude that series circuits have the following five characteristics: (1) The current flowing through each resistor is equal. Because in a DC circuit, the current intensity is the same across all cross-sections of the same branch. (2) The total voltage (the voltage across a series circuit) is equal to the sum of the individual voltages (the voltage across each resistor), that is, U = U1 + U2 + … + Un. This can be directly derived from the definition of voltage. (3) The total resistance is equal to the sum of the individual resistances. Applying Ohm’s law to each resistor gives U1=IR1, U2=IR2, …, Un=IRn. Substituting these into U=U1+U2+……+Un and noting that the current through each resistor is equal, we obtain U=I(R1+R2+Rn). This formula shows that if a resistive element with a resistance value of R = R1 + R2 + … + Rn is used to replace the original series circuit of n resistors, the current through this element will be the same as the current in the original series circuit. Therefore, the resistance R is called the equivalent resistance (or total resistance) of the original series resistance. Therefore, the total resistance is equal to the sum of the individual resistances. (4) The voltage across each resistor is proportional to its resistance value, because Ui = IRi. (5) The power allocated to each resistor is proportional to its resistance value, since Pi = I2Ri. Characteristics of series connection: The switch controls the entire circuit regardless of its position; in other words, its function is independent of where it is located. There is only one path for electric current to take, and the current that passes through one light bulb must also pass through the other one. If one light is turned off, the other light must also be turned off. Advantages of series connection: In a circuit, if it is necessary to control all components, a series circuit can be used for that purpose ； Disadvantage of series connection: as long as one link is broken, the entire circuit becomes open. That is, the electronic components connected in series cannot function properly. 4. Direct current: A current whose magnitude and direction do not change over time. Also known as constant current. The circuit that is thus formed is called a direct current circuit; it is a closed conductive loop composed of a direct current power source and resistors. In this circuit, a constant electric field is established. Outside the power source, positive charges flow from areas of higher potential to areas of lower potential through resistors; inside the power source, non-electrostatic forces exerted by the power source overcome the electrostatic forces, allowing the charges to move from areas of lower potential to areas of higher potential. This cycle repeats, forming a closed current path. Therefore, in a DC circuit, the role of the power source is to provide a constant electromotive force that does not change over time, thereby supplying the energy needed to generate the Joule heat dissipated in the resistors. Alternating current: An electric current whose direction and intensity (magnitude) change periodically. When the coil rotates at a constant speed in a magnetic field, an alternating current is generated within the coil, whose magnitude and direction change periodically. The alternating current in use today generally changes direction and intensity 50 times per second. The electricity used in common items such as light bulbs and electric motors is alternating current. In practice, alternating current is represented by the symbol “~”
2. Capacitance in series and parallel: C (capacitance) = Q (total charge) / U (voltage). Inductance in series and parallel: L = L1 * L2 / (L1 + L2).
3. Capacitive reactance = 1/2 * π * f * C (where C is capacitance). Inductive reactance = 2 * π * f * L (where L is the self-inductance coefficient). In a circuit, current flows sequentially through each component. The basic characteristic of a series circuit is that there is only one path for the current to flow. From this, we can conclude that series circuits have the following five characteristics: (1) The current flowing through each resistor is equal. Because in a DC circuit, the current intensity is the same across all cross-sections of the same branch. (2) The total voltage (the voltage across a series circuit) is equal to the sum of the individual voltages (the voltage across each resistor), that is, U = U1 + U2 + … + Un. This can be directly derived from the definition of voltage. (3) The total resistance is equal to the sum of the individual resistances. Applying Ohm’s law to each resistor gives U1=IR1, U2=IR2, …, Un=IRn. Substituting these into U=U1+U2+……+Un and noting that the current through each resistor is equal, we obtain U=I(R1+R2+Rn). This formula shows that if a resistive element with a resistance value of R = R1 + R2 + … + Rn is used to replace the original series circuit of n resistors, the current through this element will be the same as the current in the original series circuit. Therefore, the resistance R is called the equivalent resistance (or total resistance) of the original series resistance. Therefore, the total resistance is equal to the sum of the individual resistances. (4) The voltage across each resistor is proportional to its resistance value, because Ui = IRi. (5) The power allocated to each resistor is proportional to its resistance value, since Pi = I2Ri. Characteristics of series connection: The switch controls the entire circuit regardless of its position; in other words, its function is independent of where it is located. There is only one path for electric current to take, and the current that passes through one light bulb must also pass through the other one. If one light is turned off, the other light must also be turned off. Advantages of series connection: In a circuit, if it is necessary to control all components, a series circuit can be used for that purpose ； Disadvantage of series connection: as long as one link is broken, the entire circuit becomes open. That is, the electronic components connected in series cannot function properly. 4. Direct current: A current whose magnitude and direction do not change over time. Also known as constant current. The circuit that is thus formed is called a direct current circuit; it is a closed conductive loop composed of a direct current power source and resistors. In this circuit, a constant electric field is established. Outside the power source, positive charges flow from areas of higher potential to areas of lower potential through resistors; inside the power source, non-electrostatic forces exerted by the power source overcome the electrostatic forces, allowing the charges to move from areas of lower potential to areas of higher potential. This cycle repeats, forming a closed current path. Therefore, in a DC circuit, the role of the power source is to provide a constant electromotive force that does not change over time, thereby supplying the energy needed to generate the Joule heat dissipated in the resistors. Alternating current: An electric current whose direction and intensity (magnitude) change periodically. When the coil rotates at a constant speed in a magnetic field, an alternating current is generated within the coil, whose magnitude and direction change periodically. The alternating current in use today generally changes direction and intensity 50 times per second. The electricity used in common items such as light bulbs and electric motors is alternating current. In practice, alternating current is represented by the symbol “~”
Set the multimeter to its highest resistance setting, place the probes at both ends of the component being tested; if a resistance value is displayed, it’s a resistor. If the needle suddenly drops to 0 and then gradually rises to infinity, it’s a capacitor； If it remains 0, it is an inductor.
Appearance: The resistance value is generally milky yellow or blue； Inductors are generally green. The resistor has a shape that is thick at the two ends and thin in the middle ； The inductor has the shape of a uniform cylinder. Measure the resistance value. The measured value of the resistance is its actual value, that is, it matches the value indicated by the color bands ； The inductance’s measured resistance is generally below 10 ohms, which does not match the value indicated by the color bands. Circuit identification: The circuit symbol for a resistor is R ； The load of the inductor is L. An inductor is a component that can convert electrical energy into magnetic energy for storage, denoted by the letter L. It only hinders changes in current; for example, when a circuit is connected, the inductor tries to prevent current from flowing through it, and when the circuit is disconnected, the inductor tries to maintain the current at its original level. A resistor is a two-terminal device for which there is a definite functional relationship between the terminal voltage and current; it can convert electrical energy into thermal energy. It is represented by the letter R, with the unit being ohm, Ω.
Look at the color and characters: the middle part of the resistor is black with numbers printed on it (for example, 102 means K, 473 means 47K, and 391 means 390 ohms). The capacitor is brown or off-white, with no letters printed on it. Inductors are also mostly black and have parameters.
Even though I passed, I still need to keep learning*