Impedance is the combination of resistance and reactance of components in electronic devices. A PCB’s conductive traces cannot be assumed to be perfect conductors with zero resistance or reactance, despite our best efforts.
In the same way that the components on a PCB have some resistance and reactance, the materials used in the PCB determine its signal behavior. This article is all about impedance vs. resistance in detail.
Impedance
A source of impedance is something that interferes with or impedes. Unlike a circuit that contains a single element, an impedance circuit has several features that oppose each other to flow current. In electrical terms, impedance can be defined as the combination of resistance and reactance or as a standalone reaction.
It is impossible to have a constant impedance in any element or component. There are some phenomena related to the nature of electricity and the type of component that produce it.
Resistance
An object that resists or opposes is said to be in resistance. In electrical engineering, resistance refers to the property of things or materials that resist or oppose the flow of current through them. Therefore, it can be defined as a physical property that is almost constant in any material or circuit component.
Resistors, for example, only show their resistance properties when connected to AC and DC power supplies. About the AC power supply, it does not display any reactance properties.
No matter what the nature of the power supply is, an element’s resistance property does not change. The resistance property opposes the uniform flow of any electric current.
Impedance Vs Resistance
It is essential to understand that impedance opposes the flow of electric current in alternating motion, while resistance differs in any direction. The actual concept was as follows. The following comparison between them will help you understand all the images clearly and in detail. Basic electrical engineering terms such as impedance and resistance are well-known and significant.
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What are the affecting factors of resistance?
To determine a material’s resistance, four factors must be taken into account:
- Temperature: Temperature also influences resistance. The higher the temperature, the more excellent the opposition to an electric current that most materials offer. As a material’s temperature changes, its ability to release outer electrons changes as well. Several materials lose their resistance as the temperature rises, such as carbon. Different materials have different resistance properties depending on their type and temperature. The temperature has the least significant effect among the factors that affect resistance.
- Length of material: Conductor resistance also depends on the size. It is widely believed that a conductor’s length determines its resistance. By holding on to their outer electrons, atoms resist electron flow within a material. Conductor length increases when resistance is doubled in a circuit.
- Cross-Section Area: Cross-sectional area is another factor that influences resistance. A material with a lower resistance will have a larger cross-sectional area. When a wire has a larger cross-sectional area, twice as much current passes through it as a wire of the same length.
- Nature of Material: Other factors that influence resistance include cross-sectional area. Choosing a material that gives up its outer electrons readily is essential to determining its resistance.
What is the effecting factor of impedance?
Frequency is the most critical factor affecting the impedance. An AC circuit’s total impedance is partially determined by capacitance and inductance. The AC reverses direction at a frequency (cycles per second, Hz) that affect capacitance and inductance. As the frequency (f ) multiplied by the inductance, impedance increases indirectly with frequency, and the product of frequency and capacitor increases indirectly with impedance.
Series Impedance Frequency
Series RLC circuits show the following behavior with respect to their reactance:
Starting at very low frequencies, XL is low, and XC is high, indicating that the circuit is primarily capacitive. XC decreases with increasing frequency, whereas XL increases until XL = XC, at which the two reactances cancel, making the course resistive. Due to the fact that XL becomes greater than XC as the frequency increases, inductive circuits are dominated.
Frequency in parallel impedance
It is ideal for a parallel resonant circuit to have an infinite impedance. The curve indicates that maximum impedance occurs at the resonant frequency, with decreasing impedance at lower and higher frequencies.
The total impedance of a system is essentially inductive at very low frequencies because XL is very small and XC is very high. Frequency increases are accompanied by increasing impedance, and the inductive reactance dominates at resonant frequencies. The impedance decreases as the frequency goes above resonance due to capacitive reactance dominating.
Power used by resistance
Because the resistance of the circuit dissipates some power, more energy is taken from the supply than fed back into it in an electric circuit. The power consumed in a DC circuit can be calculated by multiplying its voltage by its current since, in a DC, the voltage and current are in phase with each other.
Power used by impedance
The source of emf supplies energy to the circuit, capacitive and inductive elements store it, and resistive elements dissipate it. According to this principle of energy conservation, power must be supplied by the source of emf at the same rate; it is stored in electric fields and dissipated in resistive areas at the same rate. Inductive and capacitive components are assumed to have zero internal resistance.
Adding capacitors and pure inductors to an AC circuit does not result in power losses. A pure capacitor or inductor can’t have any resistance or inductance.
Whenever the current in an AC circuit increases in one direction, a voltage drop appears across the capacitor in an impedance circuit.
Nevertheless, the charge stored in the capacitor is momentary since it returns to the source of voltage when the current reverses.
Half of every cycle is dedicated to charging the capacitor, while the other half is dedicated to returning the charge. The source, therefore, provides zero average power. As a result, AC circuits have no power losses in capacitors.
In the same way, a current-carrying inductor is subject to the back emf of the source. As the current reaches its maximum value, the inductor releases its stored energy.
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FAQs (Frequently Asked Questions)
Does resistance have a relationship with impedance?
If DC is connected to an ideal resistance, it will change with frequency. Inductance and capacitance oppose AC electricity, so impedance is the measure of their strength.
In a circuit, what role does impedance play?
The effects of impedance on circuit performance can be remarkably adverse if it is not handled correctly. Reflections can occur along the path between the source and load without proper impedance matching.
