Electricity, voltage, current and Resistance

Electricity, this is the first thing to study in electrical or electronics study. Electricity. When beginning to explore the world of electricity and electronics, it is important to start by understanding the basics of electricity and its related terms which voltage are, current, and resistance. These are the three basic building blocks required to utilize electricity. At first, these concepts can be difficult to understand because we cannot “see” them. One cannot see any electrical parameters with the naked eye. We cant see energy flowing through a wire or the voltage of a battery sitting on a table. In order to detect this energy transfer, we must use measurement tools such as multimeters to know what is happening with the electricity in a system. However, this tutorial will give you the basic understanding of voltage, current, and resistance and how the three relate to each other.

What is Electricity?

Electricity is all around us. We use electricity to give powerto our TV’s, computers, lights, mobile phones, refrigerators and oven and everything at our home. It’s not possible to imagine our day to day life without electricity, especially when power fails for some minutes or few hours, we get panic because it seems the world has stopped when electric power is not available at home. But what exactly is electricity? This is a very complicated question;in simplest words, electricity, is the form of energy which can be flown through the electronics present in an atom

In this tutorial we’ll focus on current electricity, it is the thing that powers our electronic equipments. Our goal is to understand how electricity flows from a power source through wires, lighting up LEDs, spinning motors, and powering our household devices.

Current electricity is the form of electricity which makes all of our electronic and electric devices work. This form of electricity exists when charges are able to constantly flow. As opposed to static electricity where charges gather and remain at rest, current electricity is dynamic; charges are always moving.

The definition of electricity is the flow of charge. Usually our charges will be carried by free-flowing electrons present in an atom. Negatively-charged electrons are loosely held to atoms of conductive materials. With a little push we can free electrons from atoms and get them to flow in a generally uniform direction.A closed circuit of conductive material provides a path for electrons to continuously flow.We need a source of electric potential (voltage), which pushes electrons from a point of low potential energy to higher potential energy.


The most common terms we discuss in studying electricity is voltage. A voltage is the difference in potential between two points in an electric field. Voltage gives us an idea of just how much pushing force an electric field has compared to the other point where there is no electric potential. We define voltage as the amount of potential energy between two points on a circuit. One point has more charge than another. This difference in charge between the two points is called voltage. It is measured in volts, which, technically, is the potential energy difference between two points. The unit of measuring voltage is VOLTS. Voltage between two points can be measured with an instrument called Voltmeter, or you can also use the voltmeter mode available in Multi meters. To know more about multi meters, click here


When there is a potential difference between two points in an electric field, if some path is available for electric energy to flow from higher potential point to the lower potential point, then electric energy flows through this through the available electronics in the conductor, this flow of electrons is called as Current, or electric current. The unit of measuring current is AMPERE. Currents in circuit can be measured using an instrument called Ammeter or ammeter mode in multi meter. To know more about multi meters, click here


When there is a potential difference between two points, and some path is available for electric energy to flow from higher potential to the lower potential, this path, from which current has to be flown always shows some oppose to the current flow, this is called as Resistance. Even good conductor like copper has some very little resistance associated with it, and resistance increases as the length of conductor increases. Due to this resistance offered to electricity, various interesting effects can be seen, and hence, there are some resistance offering component specially made for specific resistance values, these are called as RESISTORS. Resistance is always measured in Ohms (symbol Ω )Read More about resistors here.

Resistance is given by a simple formula

R = V / I


When describing voltage, current, and resistance, a common example is a water tank. In this example, charge is represented by the water amount, voltage is represented by the water pressure, and current is represented by the water flow. So for this example, remember

    Water = Charge

    Pressure = Voltage

    Flow = Current

The pressure at the end of this pipe can represent voltage. The water in the tank represents charge. The more water in the tank, the higher the charge, the more pressure is measured at the end of the pipe so more is the voltage.

We can think of this tank as a battery, a place where we store a certain amount of energy and then release it. If we drain our tank a certain amount, the pressure created at the end of the pipe goes down. We can think of this as decreasing voltage, like when we play games in mobile for long time, the batterygets low and eventually, phone turns off. There is also a decrease in the amount of water that will flow through the hose. Less pressure means less water is flowing. Here the flow means our current.

Now if the water flows through this pipe ending to some place down there, we say current is flowing and if it continues to flow forever, there will once come a point when the water in the tanks is over and nothing will flow from the pipe (remember the case when phone battery gets, down, tanks is empty and no current is flowing so our phone is Dead!!!)

Now imagine below

As shown in above figure, the size of the pipe is the total resistance offered to the water flow. If the pipe is larger, it means it will not resist the water flow means less resistance. And if the pipe is narrow, the water flow will be less. This is exactly similar to the resistance. If resistance is Less, more current flows in circuit and if resistance is More, less current flows in circuit.

Alternating Current and Direct Current

Note that these are the basics of how current electricity flows, but have you seen this?

What is this? A simple 3 pin socket that we see in our homes. Right?

This is the socket of the electric power that comes to our home from the mains line. This is a

  • 230 Volt
  • 50 Hz
  • AC Supply

Confused? Let’s see each concept one by one

AC stands for Alternating Current. The supply which comes to our homes through the main line is always AC supply, by the name it means that the polarity (yes, positive and negative) of this supply is continuously changing as time changes and its voltage is 230v. DC supply as compared to AC is the one in which the voltage value never changes and remains constant at a fixed voltage. The cells that we use in Remote Controls or in the wall clocks provide a constant DC voltage, to simply visualize this thing look at the below figure

Here the green line shows how the AC is alternating above and below the reference line, where as DC is a straight line providing a very constant voltage continuously.

The reason for having AC in our house hold supply is very simple. At those times, DC voltages were not that popular and almost all the devices were using AC very effectively to carry out their work, for example the Lamps, Tube light etc… so it was standardized that the supply provided will be AC and if DC is required, it will be taken from suitable DC power Sources. Next we’ll see what are DC power sources available to power our small electronic circuits

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