What is electricity

Have you ever wondered what is the thing that charges your iPad or lightens up the bulb in your room? This phenomenon is called electricity and with the passing years, it has become one of the essential things for human survival along with air, water, food, and shelter. Electricity is the phenomenon that has the steering of the car called earth because in today’s world, without electricity no human would be able to survive.

Electricity can be simply defined as the flow of negative charges, electrons, is known as electricity and it is based upon a very simple scientific fact that when electric charges move, either positive or negative, they produce an electric field and exert a force on each other. Electric can be broadly segregated into two types, that are alternating current, also known as AC and direct current, also known as DC. The main reasons they both are differentiated from each other are:

  1. The direction in which the current flows because basically the alternating current, as the name suggests keeps alternating from one direction to other, but it should also be noted that the frequency at which it alternates is fixed. On the other hand, the direct current is direct in nature and moves only in one direction or we should stay is static with its direction.
  2. The way they both are produced is quite different since different methods are used to manufacture and transmit huge amounts of alternating and direct currents.
  3. The pictorial representation of both is also quite different because when we look at the graph of an alternating current, we can see that it resembles of a sinusoidal wave that keeps on changing its direction with one held in the positive plane and the other in the negative place and hence the name is alternating. On the other hand, the graph of a direct current is more like a unit step function which is mostly a straight line and there is no change in the direction of the same.
  4. There are ways to convert an Ac current to a DC and vice versa. To convert from DC to AC, we use an inverter to do the same and try to achieve the best sinusoidal output that we can in order to achieve maximum efficiency. To reverse the process, that is to convert AC to DC, we use a device called rectifier that uses small semiconductor components known as diodes which work on the phenomenon of PN junction and block the positive or the negative half of the AC wave according to the specific needs and give us a somewhat rectified direct current output.
  5. One other factor that majorly separates the both of them is the safety that they both offer. Some countries across the globe prefer to use AC as their primary source in the household and some prefer to use DC. This is an evergreen debate and people will continue to discuss the same.

The most basic unit of electricity is known as Coulomb and was discovered by Charles Augustin De Coloumb who was also the one to give the coulombs law which states that each and every object in this universe attracts others and the force is directly proportional to the product of the masses between them and inversely proportional to the square of the distance between them. Since the charge on one coulomb is really small, it is measured with regard to the charge on an electron and hence the number of electrons in one coulomb, there are a number of 6.24 x 10^18 electrons have 1 C of charge.

To acknowledge the way electricity travels from one point to another, we need to understand the concept of potential difference because this is the basic means of transporting electricity from one point to another.

To understand the concept of potential difference let us assume that there are two tanks connected by a pipe and one tank is filled more than the other, what will happen is that the water from the tank having more water will flow to the tank having less water and result in both of them having the same amount of water and this will happen on both sides. Now, we have to imagine the same case with electricity and this is how the electricity travels from one point to another. The potential difference is defined as the difference in electric potential between two points of electricity. The standard unit to measure the potential difference between two points is known as voltage and is shortly written as V.

A major thing about the potential difference is that when there is a difference in the potential to two points, it gives rise to a force known as the electromotive force, this is the principle that runs most of the motors and the generators around the world. There has always been a misconception that electromotive force is a physical force, NO! It certainly is not. It is the force required to move a unit charge from the negative end of the generating source to the positive end multiplied by the number of charges present.

Electrical resistance, reactance, and impedance:

Hoping that the readers are familiar with the concept of conducting material and nonconducting materials, the electrical resistance can be defined as the amount of resistance that a conductor offers when a current is passed through it. In simpler words, let’s suppose that we connect a wire to a 5v  source and measure the voltage across the same, the result would be always less than 5 because there is some resistance in the wire, here we say that the wire is acting as a resistance for the voltage source. I know that you all must be thinking that resistance is a bad thing for electricity to which I would reply no because it is the thing that also becomes a safety net for our devices because the high amount of current and voltage can burn our precious and expensive devices and electrical components. The basic unit to measure the resistance is OHM and there is a very famous law known as the ohms law which states that the voltage in any conductor is directly proportional to the product of the current passing through the same and the resistance of the conductor. V= IR is the basic formula of ohms law where V symbolises the voltage in the conductor, and I and R are the current and the resistance for the same simultaneously.

Reactance: It can be considered as a synonym for the resistance, just slightly different from the same. Resistance restricts the flow of the charge from one end to another, in a similar way reactance also opposes to a change in the current or voltage of a circuit.

Impedance: Impedance can be thought of as the grand total of the total restriction that is offered to the voltage by the wire to reach from one end to other is known as the impedance of the wire. It is basically the arithmetic sum of the resistance as well as the reactance that is offered by the circuit.

Resistivity and conductivity: resistivity is something of a characteristic than a phenomenon. To understand the same, let’s  take examples of various kinds of cars, a small one, and a race car and compare their speed. I know you must be thinking that the race car will be faster because of the qualities that it has and the material that it is made of like the engine characteristics or the tires or the fuel. The same way we can understand the resistivity of the resistance of the material it is made. Each and every material has their own resistivity, some have less and some have more and the total resistance offered by the conductor is proportional to the amount of the resistivity offered by the same. There are many factors along with the resistivity on which the total resistance of the conductor depends, what are the length and the area of the conductor as well. The basic unit of resistivity is ρ(rho) and is different for different kinds of material. The net resistance of any conductor is directly proportional to the length and the specific resistivity of the same and inversely proportional to the area of the conductor. The exact opposite of resistivity is conductivity and the value is the reciprocal of the value of resistivity, i.e we divide one by the resistivity to get conductivity and it is the exact opposite of what resistivity does. It is denoted by a geek work kappa.

Electrical power: the amount of power an electrical circuit provides per unit time is known as the electric power of the circuit. The international standard unit of power is watt, that is joules per second. To understand it in simple words, it means that the circuit is able to transmit a power of one joule per second from the negative side of the circuit to the positive side.

Capacitance: When two metal plates are kept at a distance and a medium is placed between the two plates, this type of electronic device is known as a capacitor and it has a property that when charge is passed through it, it has a tendency to store charges and this phenomenon is very useful in the field of electric and electronics products. The amount of charge that the capacitor can store per unit charge passed through it is known as the capacitance of the capacitor and it is dependent on factors like the medium used between the plates and is directly proportional to the distance between two plates.

Electric field strength: As discussed earlier electrical field, that is the field created by any moving charges around the conductor it is moving is known as the electric field and the electric field strength is the expression for the magnitude of the strength of the field at specific target points. The capacitance of the capacitor depends on the material because each and every material have a different kind of permittivity and hence, will have different capacitance since they both are directly proportional to each other.

Electric susceptibility: it is known for a fact that when an electric/ dielectric material is brought in the range of an electric field, it experiences some amount of polarization and electric susceptibility is that property of the material that tells the amount or we can say the degree to which the substance will get polarized is known as the electric susceptibility of the substance. There are various factors on which it can depend, some of them are as follows:

  1. P = polarization density of the substance.
  2. Absolute permittivity
  3. The strength of the magnetic field in that specific area.

Magnetic susceptibility and induction: Just like when a dielectric material is brought near an electric field and it experiences some amount of polarization, similarly when a magnetic material is brought near another magnetic field, it experiences some degree of force and the amount of force it experiences depends on the magnetic susceptibility of the material. Induction means nothing just when an element gets heated by the magnetic forces from the current moving in a wire, it is known as heating by induction.

Sample Assignment on Electricity

Assignment # 1 – Power Consumption

Power Consumption Research


Energy is one of the fundamental elements of electricity, how energy is measured and in which units is characterized is main goal of this activity. Energy generation and delivery companies charge users of electricity by measuring the amount of power consumption (watts/hour). It is important to learn this basic unit of measurement and how is applied on building science.


  1. You must select a real dwelling unit (home, apartment or commercial building) to conduct a research activity.
  2. Through the web get an order of magnitude of the power consume by devices founded at home or dwelling unit of your choice. Example: computer / laptop, Toaster, dryer, mid-size HVAC system
  3. List and complete the information the devices founded according with following table template:


    Device Description

    Voltage (V)

    Current (I)

    Power (Watts)

    Power Calculated

    Notes: If no Power (Watts) value is found on the device but current (Amps) is found a “Power Calculated” can be obtained (Column 6)

  4. Calculate the constructed area of the dwelling selected (e.g. including Basement or second floor if the dwelling is a two-storey house)
  5. Calculate the total Power installed at the dwelling by adding the power of all devices founded and estimate the total power consumption per year Kilowatt/hour (Please make assumptions for power consumption, e.g. 4 hours per week of dryer utilization)
  6. Calculate the Total Power Consumption per year for the dwelling of your choice.

    Note: Please make your assumptions if Power Consumption is not known for the HVAC or any Heating System or Cooling system applied on winter and summer time.

  7. Write a complete report and make your own conclusions about devices that consume more power at dwelling selected.
  8. Post your findings and listing results on the BlackBoard (BB)


The Assignment will be evaluate on the following items:

  • Report format and organization
  • Elaborate research and presentation of findings
  • Developed content on conclusions provided

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