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Chapter 8 – Electric Power

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:


Our lives are convoluted with the wonders of electricity. Accessibility to near and far possibilities has been made possible with the invention of electric power. Have you ever wondered how and what electric power is? It is easily one of the most revolutionary inventions of our times. Without electricity, you won’t be able to read this right now. Let’s learn the basics, principles, and importance of electric power as we go through this article.

Where have we seen electricity? When we switch on a bulb, we see it when we use an electric water pump to receive water, when we use our mobile phones, etc. All the above examples use electricity for their functioning. A light bulb switch, when turned on, uses a closed circuit to pass the electric current to the light bulb, which further lights up.

Electric current is the rate of flow of the electric charges through a particular area per unit of time. It is the rate at which electric charges flow through the system. Likewise, an electric circuit is made up of electrically conducting metallic wires in a loop. When the circuit is complete and closed, the electric current passes through the circuit’s metallic wires, making the device ready to use. 

Let’s go back to the previous example. When we say a light bulb is lit after its switch is turned on, that effectively means that the electric circuit is closed, and since it is closed-circuit, the current passes through to it, resulting in lighting the bulb. The direction of the electric current is in the opposite direction of the flow of electrons. If the net electric charge flowing through a circuit cross-section is “Q” in time “t” then, the current flown through the cross-section of the closed system is given as:

I= Q/t

SI unit of electric current in Coulomb (C) = equivalent charge of 1.6 x 10-19 C.

Electric potential is expressed as the work done in carrying a positive unit charge from one end (considered to be infinity) to the reference point.

V = W/q

V= electric potential

W = work done

q = electric charge

SI unit of electric potential is Volts (V)

Between two points of a circuit, the electric potential difference is the work done in carrying a unit of positive electric charge from one point to the other.

V = W/Q

Where V= electric potential difference

W= work done

Q= Charge

The SI unit of potential difference is Volts (V), named after the scientist Alessandro Volta.

1 Volt = 1 Joule/ 1 Coulomb

The formula is 1V = 1 J C-1. Potential difference is measured using Voltmeter.

We all know that for electricity to pass through, a circuit is needed. For understanding purposes, these circuits are presented in the form of diagrams. Lines denote conducting wires; symbols denote various components used in the circuits such as bulbs, voltmeter, ammeter, and others. Let’s look at the following table.

This famously used law was given by Georg Simon Ohm in 1827. Ohm’s law states that any electric current that flows through a metallic wire is directly proportional to the electric potential difference V, across its ends provided its temperature remains equivalent. In simple words, the potential difference is proportional to the current.

Where V= potential difference

I = electric current 

R = constant also considered the resistance of the conductor. 

Resistance is a property of the conductor to resist the flow of current. The higher the resistance, the lower will be the electric conductance of the conductor. 

SI unit of resistance is Ohm. 

The formula of resistance is R= V/I.

Hence, 1 Ohm = 1 Volt/ 1 ampere. 

Some characteristics of the resistance property of a conductor are 

  1. It is dependent on the length of the conductor.
  2. It is dependent on the nature of the conductor.
  3. It is directly dependent on the temperature of the conductor.
  4. It is inversely dependent on the area cross-section of the conductor.

In a circuit, resistors can be present as a system of resistors in series or parallel. 

The resistance of a system of resistors in series: In series, the total potential difference is the sum of individual potential differences of the conductors. Hence, the formula is 

Vtotal = V1 + V2  + V3 +…. Vn

Since R is directly proportional to the potential difference 

Rtotal = R1 + R2  + R3 +…. Rn

The resistance of a system of resistors in parallel: In parallel, the total current is the sum of the individual current of the conductors. Hence, the formula is 

Itotal = I1 + I2  + I3 +…. In

Since R is inversely proportional to the current, 

1/Rtotal = 1/R1 + 1/R2  + 1/R3 +…. 1/Rn

The heating effect of electric current is understood using Joule’s law of heating

H = I2 Rt

The heat produced when a current I passes through a conductor with resistance R in time t. 

Power is defined as the amount of work done within a particular time. Electric power is understood as the rate of flow of electric energy that passes through a closed electric circuit per unit of time. Electric power is denoted using P, and its SI unit is Watt. We express a watt as Joule per second or J/sec or, in other words, 1 Watt is the power consumed by any object/device that carries 1 Ampere of current at a potential difference of 1 volt.

P = VI

Or P = I2R = V2/R

As Watt’s unit is small when put to use, we often use Kilowatt for technical purposes. 1 KW is equal to 1000W. Hence the commercial unit of electric energy is expressed as KW H (Kilowatt Hour).

  1. What is the electric power formula?

Answer: Electric power formula is P = VI or P = I2R = V2/R, where, P= electric power, V= Potential difference and I = electric current.

  1. What is electric power class 10th?

Answer: Electric power for class 10 discusses electric current, electric circuits, potential difference, resistance, ohm’s law, and others. It covers the basics of electricity. 

  1. What are the types of electric power?

Answer: Electric powers are with AC(Alternating Current) or DC(Direct Current). 

  1. What is the difference between electric energy and electric power?

Answer: The basic difference is that electric energy is a form of energy represented in Joules, and electric power is the amount of electric energy generated per second. SI unit of electric power in Watts (W). 

  1. What is the commercial unit of electric power?

Answer: Since Watts is a relatively smaller unit, for commercial purposes, Kilowatt (KW) is used.

To learn more about the working of electricity and electric circuits, visit the MSVgo application or website. It is a digital video library that explains concepts using visualizations and animals, which are visually appealing and explanatory. The specialized Maths-Science Video application/website provides fully explained concepts with examples that give you a sense of understanding of the textbook stuff and learning experience, which is uncommon these days. The motto of MSVgo is to provide core concepts to everyone. It is easily accessible and provides umpteen content in every subject for everyone.

High School Physics

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Middle School Science

  • Acids, Bases And Salts
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Middle School Math

  • Addition
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