Active passive elements are very important for us electrical engineer. What are those actually?
For short, an active element is capable of delivering energy to an electric circuit, while a passive element is an element that is not capable of generating power.
After learning what an electric circuit is, you may have some questions about what are the element circuits. You found the names of the resistor, inductor, capacitor, and many more in my previous explanation.
But what are they actually?
If you try to find the meaning behind ‘what is electric circuit element’, you will mostly find difficult explanations along with difficult examples.
Yes, when I read about what electric circuit elements are, I made myself more confused and needed to read from several sources.
But, worry not! I will give you the easiest explanation about what a circuit element is, so you will only need to read from here and not anywhere else.
Let’s start from the very basic elements we will use ALMOST EVERY TIME.
Basic Circuit Elements
When you read basic circuit elements, you must think about resistor, capacitor, and inductor. Well, it is not wrong, but it isn’t the ‘perfect answer’.
Rather than mentioning the elements, it is easier to mention the types of circuit elements.
We will start the explanation of the types right after this. We will still find the resistor, inductor, and capacitor below, but we will expand our knowledge at the same time.
Not only mentioning the elements, but we will also learn about their functions, their shape, and their applications.
Types of Electric Circuit Components
Electric circuit elements can be divided into several categories, such as the number of ports, active or passive, and linear or nonlinear.
We will focus on active and passive elements, but it is not hurt to give brief explanations about the other types.
Circuit Element Ports
We can divide the circuit element by their number of ports, such as:
 Oneport elements: this type of element is the simplest one. This element only has two terminal which can be connected with another element. The examples of this type are resistors, inductors, and capacitors.
 Multiport elements: unlike oneport elements, this type has more than two terminals. These elements connect to circuits with multiple terminals (ports). An example of this type is a 3winding transformer (6 ports).
Circuit Element Linearity
This type will divide circuit elements into linear and nonlinear elements.
Linear: this type of elements follow the linearity between voltage and current. The examples of this type are resistor, inductor, capacitor, and dependent source.
These elements will not cause distortion and can be analyzed easily. The examples of linear components are resistor, capacitor, and inductor.
Linear Component – Resistor 
Linear Component – Inductor 
Linear Component – Capacitor 
Nonlinear: this type of elements will follow the nonlinear relationship between voltage and current. This element will cause distortion and the example of it is a diode.
You will find it harder to analyze this type of element.
Nonlinear Component – Diode 
Active and Passive Elements
If you wonder what the most common types of circuit elements are? Well, we will talk about active and passive elements. What is the difference between these two? These two types of element will form the node, branch, and loop to make a complete circuit.
One thing to remember, their difference lies in the capability of generating energy. Active and passive elements is a serious matter to analyze in a circuit. These elements will take part on Ohm’s law explanation in later post.
Active element
Active elements can be used for electrical power sources, such as voltage source and current source.
Active element is capable of producing electrical power and its role is to amplify an input signal to be a larger output signal.
The examples of active elements are voltage source, current source, transistor, diode, and generator.
An active element is an electrical component which is capable of delivering energy to an electric circuit.
Active elements have the capability of controlling electron flow. We need at least one active component to make a circuit work.
If you ask what the most important active elements are, the answer is voltage and current source. These two are able to deliver power to the circuit.
The voltage and current source can be divided again into 2 types: independent sources and dependent sources. We will learn this in the next session.
Passive element
Passive elements are often used as a load for a circuit. Its capability on storing energy, resisting voltage or current, and absorbing energy gives us a huge choice on designing an electric circuit. The most basic passive elements are resistor, capacitor, and inductor. While we can divide the resistor into resistor in series or resistor in parallel. We can do the same with the capacitor and inductor.
Summary,
Passive element is an element that is not capable of generating power. But, this element absorbs, stores, or dissipates energy flowing to it.
This can be represented as a load. The most common examples of passive elements are resistor, inductor, and capacitor.
Independent Sources
We will assume that the independent source is in ideal condition. Summary,
Ideal independent source is an active element that is able to generate a determined voltage or current which is fully independent to other circuit elements.
The Independent voltage source is an active element that generates determined voltage completely independent of the current flow in a circuit.
For a more specific definition, we can say:
An ideal independent voltage source is able to deliver how much required current to the circuit to maintain the terminal voltage.
The examples of ideal independent voltage sources are generators and batteries.
The symbol in Figure.(1) represents an independent voltage source. Those two symbols can be used to represent dc voltage source but the only symbol in Figure.(1a) can represent ac voltage source or timevarying voltage source.
Figure 1. Independent voltage source symbols 
Independent current source is an active element that generates determined current completely independent of the voltage across the source.
Similarly,
An ideal independent current source is able to deliver how much required voltage to ensure the stated current flow.
The symbol of independent current source i can be illustrated in Figure.(2) where the current flow direction is indicated by an arrow.
Figure 2. Independent current source symbol 
Dependent Sources
After learning about independent sources, we will learn about the dependent source. Like before, we will use ideal conditions for the source.
An ideal dependent source (controlled source) is an active element that its source value and quantity is dependent (or controlled) by another variable (voltage or current).
As you can see in Figure.(3), the dependent sources are illustrated in diamond shape symbols. Figure.(3a) represents a dependent voltage source and Figure.(3b) represents a dependent current source.
The symbol itself is presented by diamondshaped symbols in Figure.3 where Fig.3(a) is a dependent voltage source and Fig.3(b) is a dependent current source.
Figure 3. Dependent source symbol 
There are four possible types of dependent sources depend on the voltage or current controlling the source :
 Voltagecontrolled voltage source (VCVS)
 Currentcontrolled voltage source (CCVS)
 Voltagecontrolled current source (VCCS)
 Currentcontrolled current source (CCCS)
Dependent sources are very useful for modelling purposes of transistors, operational amplifiers, or integrated circuits.
The example of a currentcontrolled voltage source is shown in Figure.(4) at the right side where the voltage 10i depends on current i through element C.
Figure 4. Current controlled voltage source 
Must be noted that voltage source (dependent or independent) will deliver any required current to maintain the terminal voltage as stated.
For the same idea, the current source will provide the required voltage to ensure the stated current flow.
Keep in mind that you will find these element for both DC circuit and AC circuit.
Circuit Elements Examples
To understand the explanation better, let us review the examples below :
1.Determine the absorbed power or supplied power for each element in Figure.5
Figure 5. Example of the currentcontrolled current source 
Solution:
For p1, the 5A current is out the positive terminal, then
p1 = 20 (5) = 100 W → Supplied Power
For p2 and p3, the current flows into the positive terminal, then
p2 = 12 (5) = 60 W → Absorbed Power
p3 = 8 (6) = 48 W → Absorbed Power
For p4, take note the voltage is 8 V with a positive terminal at top same as the voltage of p3. Since the current flows out of the positive terminal, then
p4 = 8 (0.2I) = 8 (0.2 x 5) = 8 W → Supplied Power
We should observe that 20 V independent voltage source and 0.2I dependent current source are supplying power to the rest of the network, while the other 2 absorbing power, then
p1 + p2 + p3 + p4 = 100 + 60 + 48 – 8 = 0
Applications
TV Picture Tube
The application of the motion of electrons can be found in both the transmission and reception of TV signals. TV camera reduces a scene from an optical image to an electrical signal at the end of transmission end.
The scanning process will occur with a thin beam of electrons in an iconoscope camera tube.
At the receiving end, the image is constructed using a cathode ray tube (CRT) located in the receiver. The CTR is represented in Figure.6.
When iconoscope tube produces an electron beam with constant intensity, CRT beam varies in intensity depending on the incoming signal.
Figure 6. Cathode ray tube 
The electron gun at high potential fires electron beam. The beam passes through two pairs of plate both vertical and horizontal deflections so the spot on the screen where the beam strikes can move right, left, up, and down.
After the beam hit the fluorescent screen, it gives light to that spot and a picture is shown on the TV screen.
Electricity Bills
The second application to deal with is electricity usage which charged by the electric utility company to us, customers. The cost depends on how much energy we consumed in kilowatthours (kWh).
However, if a customer does not use energy at all, there is still a minimum payment charge to the customer to pay as connecting electricity service.
The interesting thing is, as the energy consumption rises, the cost per kWh will drop. Let us see the Example below :
2. A family consumes 700 kWh in February. Calculate its electricity bill with a residential rate schedule below :

Base monthly charge : $12.00

First 100 kWh per month : 16 cents/kWh

Next 200 kWh per month : 10 cents/kWh

Over 300 kWh per month : 6 cents/kWh
Solution :
$12.00 = Base monthly charge
$16.00 = First 100 kWh @$0.16/kWh
$20.00 = Second 200 kWh @$0.10/kWh
$24.00 = Remaining 400 kWh @$0.06/kWh
$72.00 = Total charge
Average cost = $72 / 600 = 10.2 cents/kWh
Problem Solving
The steps will be :
 Define the problem carefully.
 Present everything you know about the problem.
 Establish a set of alternative solution and decide one which has the greatest chance of success.
 Attempt a problem solution.
 Evaluate the solution along with the accuracy.
 If the solution is satisfactory, present the solution; if not, repeat from step 3.
Read the explanation below :
1. Define the problem carefully. This first step is the most important part of the process because it becomes the foundation for all the steps.
In a simple explanation, you need to understand the problem completely. Make your time to identify the problem with some help from any individual relatedfield.
2. Present everything you know about the problem. Write down every possible methods or solution you know.
3. Establish a set of alternative solution and decide one which has the greatest chance of success. Every problem will have a number of the path to find the solution, so it is wise to find any alternative possible help to save your time and stress, including software packages which may help you greatly along with high accuracy.
4. Attempt a problem solution. This is the time to begin solving the problem. Any attempts must be well documented in order to find a successful solution or to revise the unsuccessful. The detailed revision may be the best solution for the problem and even simpler alternative solution.
5. Evaluate the solution along with the accuracy. Evaluate deeply about the solution, is it worth to present to your boss, team, or whoever it is?
6. If the solution is satisfactory, present the solution; if not, repeat from step 3. Proceed with the presentation of the solution or revise it once more if it leads to other problems or alternatives.
Frequently Asked Questions
Now we will find some answers to the most frequently asked questions about this topic:
What are the 3 elements of electricity?
It is easy to mention the 3 basic elements of electricity, they are electric current, electric voltage, and electric circuit.
What are the basic electrical elements?
When designing and building an electrical circuit, you will mostly use: resistor, inductor, capacitor, transistor, diode, and integrated circuits.
What are active and passive circuit elements?
Active elements mean an element that is able to generate power to an electric circuit. But, passive elements mean otherwise, they are not capable of delivering power. These elements are only absorbing or storing energy.
What is an ideal independent source?
The ideal independent source is an active element that is able to generate a determined voltage or current which is fully independent to other circuit elements.
What are the different types of dependent or controlled sources?
There are four possible types of dependent sources depend on the voltage or current controlling the source :
voltagecontrolled voltage source (VCVS)
currentcontrolled voltage source (CCVS)
voltagecontrolled current source (VCCS)
currentcontrolled current source (CCCS)
How do you solve a dependent source in a circuit?
We can use almost every analysis method to solve a circuit with dependent sources. But, the most known method is nodal analysis.
Have you understood what is the circuit elements? Don’t forget to share and subscribe! Happy learning!
Reference: Fundamentals of electric circuits by Charles K. Alexander and Matthew N. O. Sadiku
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