Electric Circuit Fundamentals
The Fundamental knowledge and skills of the basic electrical circuits always work as a strong foundation for technically sound experience. Students can also become vigorously familiar with these basic circuits particularly with hands-on experience. The basic circuit thus helps a learner to gain understanding of the basic components and circuit’s characteristics while it is in operation.
This article gives fundamental concepts about two types of electric circuits: AC and DC circuits. Depending on the type of source, electricity varies as Alternating Current (AC) and Direct Current (DC).
Basic DC circuits
In DC circuits, electricity flows in constant direction with a fixed polarity that doesn’t vary with time. A DC Circuit uses steady current components like resistors and resistor combinations; transient components like inductors and capacitors; indicating meters like moving coil voltmeters and ammeters; power supply battery sources, and so on.
For analyzing these circuits, different tools like ohms law, voltage and current laws like KCL, KVL, and network theorems like Thevinens, Norton's, Mesh analysis, etc are used. The following are some of the basic DC circuits that express the operating nature of a DC circuit.
Series and Parallel Circuits
Resistive loads represent the lighting loads that are connected in various configurations to analyze the DC circuits that are shown in the figure. The way of connecting loads certainly changes the circuit characteristics.
In a simple DC circuit, a resistive load as a bulb is connected between the positive and negative terminals of the battery. The battery supplies the required power to the bulb and allows a user to place a switch to turn on or off according to the requirement.
The loads or resistances connected in series with the DC source, as an electrical symbols for lighting load, circuit share common current, but the voltage across the individual loads vary and is added to get the total voltage. So there is a voltage reduction at the end of the resistor compared to the first element in series connection. And, if any load goes out from the circuit, the entire circuit will be open circuited.
In a parallel configuration, the voltage is common for each load, but the current varies depending on the rating of the load. There is no problem in an open circuit even if one load is out of the circuit. Many load connections are of this type, for instance the home wiring connection.
Therefore, from the above circuits and figures, one can easily find the total load consumption, voltage, current and the power distribution in a DC circuit.
AC Circuit with a Resistor
In this type of circuit, the voltage dropping across the resistor is exactly in phase with the current as shown in the figure. This means that when instantaneous value voltage is zero, the current value at that instant is also zero. And also, when the voltage is positive during the positive half wave of the input signal, the current is also positive, so the power is positive even when they are in negative half wave of the input. This means that the AC power in a resistor is always dissipating as heat while taking it from the source, irrespective of whether the current is positive or negative.
AC Circuit with Inductors
Inductors oppose the change in the current through them not like the resistors that oppose the flow of current. This means when the current is increased, the induced voltage tries to oppose this change of the current by dropping the voltage. The voltage dropped across an inductor is proportional to the rate of change in the current.
Therefore, when the current is at its maximum peak (no rate of change in shape), the instantaneous voltage at that instant is zero, and reverse happens when the current peaks at zero (maximum change of its slope), as shown in the figure. So there is no net power dissipation in the inductor AC circuit.
Thus, the instantaneous power of the inductor, in this circuit, is entirely different from the DC circuit, where it is in same phase. But, in this circuit, it is 90 degrees apart so the power is negative, at times, as shown in the figure. Negative power means the power releases back to the circuit as it absorbs it in the rest of the cycle. This opposition of current change is called as reactance, and it depends on the frequency of the operating circuit.
AC Circuit with Capacitors
A Capacitor opposes a change in the voltage, which is dissimilar to an inductor that opposes a change in the current. By supplying or drawing current, this type of opposition takes place, and this current is proportional to the rate of change of the voltage across the capacitor.
Here, the current through the capacitor is the result of the change in the voltage in the circuit. Therefore, the instantaneous current is zero when the voltage is at its peak value (no change of voltage slope), and it is maximum when the voltage is at zero, so the power also alternates in positive and negative cycles. This means it does not dissipate the energy but just absorbs and releases the power.
AC circuit behavior can also be analyzed by combining the above circuits like RL, RC and RLC Circuits in series as well as in parallel combinations. And also the equations and formulas of the above circuits are exempted in this article to reduce the complexity, but the overall idea is to give a basic concept about the electrical circuits.
We hope that you might have understood these basic electrical circuits, and would like to have further hands-on experience on various electrical and electronic circuits. For any of your requirements, comment in the comments section given below. We are always ready to help you guide in this particular area of your choice.
Mr. Muhammad Saqib, M.Sc. (PAK), Research Fellow (PAK), a member of IEEE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from University Of Engineering And Technology Taxila, PAKISTAN.
No comments:
Post a Comment