What is Electricity?! Electricity is all around us, we use it in different forms throughout our day to day activities. The LED light above my head right now is converting electrical energy to light energy and heat energy. So how do we explain this phenomenon called electricity which is something we use every day but something we rarely see.


Electricity is nothing but the movement of electrons. Now to explain electricity, we need to talk about electrons, so what is an Electron? An electron is a charged particle which has a certain amount of Energy. Anything with Energy can be used to do work. While typing this blog I have a certain amount of energy because of the food I ate for Dinner, and that energy I am harnessing to do work (Writing this blog). In the same way, all the appliances around us use the movement of electrons (Energy of electrons) to get their work done. A light bulb, a fan, TV are all harnessing these movements of electrons.

In this blog, we will be covering 5 basic units in Electricity ie.Voltage, Current, Resistance, Power and Energy.

To explain Voltage, Current and Resistance we will be using water tank analogy.


Consider a Water Tank on top of your house, the bottom of this tank has a hose.

The water in the tank can be compared to a charge.

Fig. 1: Charge

There will be a certain pressure at the Inlet of the Hose because of the amount of Water in the tank and the pressure at the inlet of the hose can be compared to Voltage.

Fig. 2: Voltage

The pressure inside this tank at any place is defined as Potential. There will be some pressure above the water in the tank and there will be some pressure near the outlet hose. At these two points, there is a difference in pressure. The difference in the pressure between these two points is nothing but called as Voltage. Voltage is defined as the potential difference between two different points (in this water tank terminology its pressure difference).

More the water, more the pressure.

Comparing the above scenario to Voltage, Voltage is nothing but the difference in charge between 2 points, more the amount of charge, more the voltage.

Voltage is measured in Volts (V)



Now in the same scenario, when the hose is turned on, Water will start flowing out. The higher the amount of water, higher the pressure and higher the flow from the hose. The amount of water flowing from the hose is nothing but the flow of charge. This flow of charge is nothing but “Current

Fig. 3: Current

With water terminology, we measure the volume of water flowing through hose over a certain period of time. With, electricity terminology we measure the amount of charge flowing through a circuit over a period of time.

Current(I) can be defined as Rate at which charge is flowing and it is measured in Ampere(A).




When the water is flowing out (Fig. 3) if there is a narrow hose inserted between the tap and tank outlet (Fig. 4), it controls the flow of water. The amount of water flowing out of tank will be less. This is basically because of the narrow pipe. This narrow pipe is resisting the flow of water(charge). Resisting the flow of the charge is called as “Resistance.

Resistance(R) can be defined as the material tendency to resist the flow of charges. It is measured in Ohms.


Fig. 4: Resistance

Now suppose we have 2 water tanks (Fig. 5), Each tank has the exact same amount of water, but the hose on one tank is narrower than the hose on the other. When the water starts flowing the amount of water coming out from both tanks will be different, the tank with the narrower hose will have less amount of water flowing out. In electrical terms, the current through the narrower hose will be lesser than the current through the wider hose.

Fig. 5: Same Voltages with different Current


In order to make the flow in above section same (Fig. 6), we will have to decrease the amount of water (charge) in the tank with wider hose outlet, thus decreasing the pressure in the tank.Therefore the flow of water(charge) will be decreased which eventually decreases the current. In electrical terms, Voltage is directly proportional to the Current.

Fig. 6: Different Voltages with the same Current



Ohms law

From the above scenarios, we have seen that as Voltage(Pressure) increases Current(Flow Rate) Increases, and as Resistance to the flow Increases Current Decreases. Combining all these relationships Georg Ohm developed the formula:

This formula is popularly known as Ohm’s law.

Ohm’s law states that V = IR

Power and Energy

Energy and Power are the two most important concepts in Electricity for everyone. How much bill amount we pay to the electricity supply company depends on the amount of energy we use at our house, office etc. And how much energy we used depends on the power ratings of the appliances we use.

Power (Wattage) of a device depends on the Voltage rating and Current Rating of the device. It is defined as an amount of Electrical energy used in Unit time. It’s measured in Watt (W).

Power (P) = V X I

Now suppose I have a 100W fan which I am going to use for 10 hours so that total energy the fan is using is nothing but 100W * 10 hours= 1000Wh or 1kWh or 1 unit. ESCOM’s (Energy Supply COMpany) charge us for each unit we use.

Please find in the below table the energy usage of typical everyday appliance


Type of Appliance Power of the appliance Daily Duration of usage Electrical energy consumed
Tube light 40W 4 hours 40x 4 = 160 Wh
LED Tube Light 20W 4 hr 20 x 4 = 80 Wh
Fan 75 W 10 hr 750 Wh
Energy Efficient Fan 35 W 10 hr 350 Wh
TV 55 W 10 hr 550 Wh
Cooler 200 W 10 hr 2000 Wh
computer 80 W 10 hr 800 Wh
AC 1.5 kW 10 hr 15000 Wh
Gyser 2000 W 1 hr 2000 Wh

Energy used by an appliance depends on how much time we use that appliance and the number of hours we use it.  Electrical bills are usually measured in “Units.” These Units are nothing but the amount of energy consumed. One unit is defined as 1kWh (kilo Watt hour). To be more precise it is the number of Watt’s used in an hour.


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