What is the Difference Between Impedance and Resistance?
Primarily, the term “resistance” applies for Direct Currents (DC), and “impedance” is used for the Alternating Current (AC). There are different aspects involved in these terms, and it helps to understand what these are including factors that affect them. Read along to understand the difference between these two concepts.
Understanding the Concept Involving Resistance
Once electrons located in a conductor collide with the ionic lattice, resistance occurs. This instance happens upon conversion of electrical energy to heat. However, in the case of AC, this involves other processes that cause resistance such as capacitance and inductance. It is not merely created by the changing of electrical energy into another form.
When it comes to coiled wire, inductance is quite apparent. A circular magnetic field is produced around a wire as current flows in it. Once you coil a wire to form a cylindrical form or solenoid, the fields around it tend to sum up. On the inside of the wire, a uniform type of magnetic field is created.
However, with AC, the changing of the field in coiled wires also alters the solenoid’s magnetic field. An EMF is produced once the field lines start to cut across the conductor. In simpler terms, the flow of AC current through a conductor induces a small amount of back current. This leads to a reduction of the total current.
Another cause of resistance in AC current is capacitance. Electrons tend to form on the negative plate as current flows. In addition, an electric field pushes electrons on the other side of the plate, and this makes the electrons positively charged. As electrons build up on the negative plate, this also repels incoming electrons, which also changes the charge into positive. The process causes the total current to reach a zero value. Thus, the capacitance is determined by calculating the plates’ sizes and the insulator primitively.
What is Impedance?
Another important term to understand is impedance. As mentioned earlier, this concept is applicable to AC current. Generally, there are two factors included in impedance, which are resistance and reactance. There is no change that occurs with pure resistance, regardless of the frequency. This is the reason why resistance applies only with DC electricity as direct current never changes.
As for reactance, this changes with frequency. Capacitors allow DC to flow, but current immediately stops flowing once it is charged. Putting a significant amount of frequency on the capacitor will lead to an effect similar to a short circuit. Hence, capacitors come with a reactance inversely proportional to the frequency.
Impedance is caused by reactance and resistance, which are key elements for AC design and analysis. Moreover, it is regarded as an abstraction of scenarios or elements including rise times and time constants, which are complicated issues. This concept organizes various abstract and complicated scenarios to be summed up in one subject. With this in mind, impedance mainly includes reactance, with the latter involving different effects varying because of frequency caused by either capacitance or inductance.