What is electric current? For summary, electric current is the rate of flow of electrons passing through a conductor. This one parameter electrical circuit is measured in Ampere (A).
What are Electrons
Electrons are a particle in a molecular structure of a substance. This sounds too weird in an electrical terms, so let’s skip this formality for another chance. In an electrical term, electrons are particles which carry negative charges.
When the electrons are moving, the negative charges are also moving. This movement is what we call an electric current, the movement of electrons. For how much the electrons are moving, it depends on the conductor, resistance or impedance, and the load in the circuit.
Conductor is a material that is able to carry the electric current or electrons to flow from one point to another, back and forth. Conductors are mainly metal such as copper, iron, aluminium, steel.
Opposite of conductor, an insulator is unable to carry the electric current, or a material that resists the flow of electrons from one point to another. The most common examples of insulators are plastic, glass, and wood.
What are Electric Charge
Just as stated in psychic, atoms are the smallest matter consisting of protons, electrons, and neutrons. Knowing this will help us to realize the relationship between this and the electric current.
Electron is a negative charge (e) and has a magnitude of 1.602 x 10-19. To balance this, the proton carries the exact magnitude but positive charge.
Electric charge is one of the most fundamental quantities of electric circuit.
Charge is an atomic particle in electrical system, measured in Coulombs (C).
Not to make things longer than it should be, below is the key notes of electric charges:
- The Largest unit of charges is Coulomb. For every 1 C of charge contains 1/(1.602 x 10-19) = 6.24 x 1018 electrons.
- From the experiment observatory, the only charges that happen in nature are integral multiples of electronic charge e = -1.602 x 10-19 C.
- The “Law of Conservation of Charge” states that charge can not be created or destroyed, it can only be transferred from a point to another where it can be converted to another energy form.
Observe the illustration below:
What is the direction of electric current?
Theoretically, electrons are flowing from negative to positive (since it carries negative charges). But for the conventional purpose, it is agreed worldwide that the direction of current flow will be determined by the positive charge flow direction even the electron moving in the opposite direction.
One thing to keep in mind, there are no electrons flowing in the circuit if it is an open circuit, we need to close the circuit.
What are Electric Current
What is electric current?
An electric current is a flow of charges (electrons), moving through an electrical conductor measured in Ampere (A)
This can be expressed in mathematical equation, showing the relationship between electric current, electric charge, and time.
Where:
i = electric current (Ampere / A)
q = electric charge (Coulomb / C)
Looking from the equation, we can conclude that
1 Ampere is equal to 1 Coulomb / second
To calculate the amount of electric charge, we can use integral for both sides.
Looking from two equations above, we can see that the amount of electric current and electric charge are not bound to constant-value function.
There are two types of electrical current as well with electrical voltage and electrical power. They are:
A direct current (DC) is a current that has constant value with time changing. It will remain constant as long as the parameters in the circuit are not changed.
The graph below shows us the constant value of current, a direct current. The symbol of constant current or direct current is I.
Opposite to that,
An alternating current (AC) is a current that has a time-changing value since its value is affected by time (t). This electric current has both positive and negative value and it flows forth and back to the supply source.
The graph below shows us the time-changing value of current, an alternating current. The symbol is i.
The graph above is the most common alternating current, a sinusoidal alternating current. We will learn other forms on other occasions. The key point is, the values are changing based on time and it has both positive and negative polarities.
Keep in mind that both DC and AC need different electrical measurement tools.
Without using tools, we can calculate the current with circuit analysis but we need to understand the nodes, branches, and loops first.
Electric Current vs Resistance
If you have known about Ohm’s Law, you will be able to understand the relationship between voltage, current, and resistance. This is the basis of electrical circuit analysis.
Since we are talking about electric current, we will learn about its relationship with resistance.
Illustrate a pipe as a conductor in an electrical circuit. The current or amperage is the flow of the water. The bigger the diameter of our pipe, we will have faster water flow. In other words, less resistance causes more flow and vice versa.
The amount of water is the voltage (V), the flow rate of the water is the current (I), while the water tap is the resistance (R). How fast the water flow is affected directly by how much we open the tap.
Voltage source and current source are active elements (since they generate electrical energy), while resistance is passive (since it absorbs electrical energy).
Electric Current Example
For the starter of the concept, let us review these electric circuits examples below :
1. How many charges in 4.600 electrons?
Answer:
Every electron has -1.602 x 10-19 C. Thus 4.600 electrons will have -1.602 x 10-19 x 4.600 = -7.369 x 10-16 C.
2.Total charge entering one terminal is q = 5t sin4πt mC. Calculate the current at t = 0.5 s.
Answer:
3. Calculate the total charge entering a terminal for a period time from t =1 s to t = 2 s if the current is i = (3t2 – t) A.
Answer:
Frequently Asked Questions
What is the meaning of electric current?
Electric current is a flow rate of electricity in a closed electrical circuit, indicating the amount of electricity flowing in the circuit measured in Amperes (A). The larger the current (A) the more electricity is flowing in the circuit.
What is electric current in a simple circuit?
An electrical circuit is a path of electricity to flow through several electrical components. An example for a simple circuit consists of voltage source, conductors, and a resistor. This circuit needs to be a closed circuit to allow the current flowing.