Electric Current: The Flow Of Charge

Our ancestors relied on fire for light, warmth and cooking. Today at the flick of a switch, turn of a knob or the push of a button we have instant power. This is possible because of the electric current. Electric current is one of the important discoveries that helped us revolutionise the way we live. From the time we wake up till the time we sleep in the night, our life is dependent on electricity. From the television that you watch to the toaster that you use to toast bread, all run on electric current. Besides playing a major part at home, electricity also plays an important role in industries, transportation and communication. In this article, let us learn more about this important resource that we are highly dependant on.

What is Electric Current?

We can define electric current as the rate of flow of electrons in a conductor. The protons are tightly packed inside the nucleus of an atom whereas electrons in the outer shells orbits around the nucleus. Since electrons are loosely held by the nucleus, they are able to travel freely within the limits of the body. The SI Unit of electric current is the Ampere.

Electric Current

Visualizing Electric Current

Imagine an iron beam with a rectangular cross-section. Consider one single frame in this beam. Let’s visualize the flow of electrons inside the beam. Let’s consider the electron flow from the right to the left as Qnegative and flow from left to the right as Qpositive . The total resultant electrical current through the frame in the time interval ‘t’ is Qnet=Qpositive–Qnegative . Electric current is nothing net charge through the frame divided by the time interval.

I=Qnet/t

Under normal conditions, the electrons are flowing haphazardly inside the body. So the total motions of the electrons through the frame cancel out since there are the same amount going in both directions. If the electric current comes out to be negative then it means that the current is flowing in the opposite direction.

Watch this video to understand how current flows,


Properties of Electric Current

Electric current is an important quantity in electronic circuits. We have adapted electricity in our lives so much that it becomes impossible to imagine life without it. Therefore, it is important to know the properties of electric current. The listed below are a few properties of electric current:

  • We know that electric current is the result of the flow of electrons. The work done in moving the electron stream is known as electrical energy. The electrical energy can be converted into other forms of energy such as heat energy, light energy, etc. For example, in an iron box, electric energy is converted to heat energy. Likewise, the electric energy in a bulb is converted into light energy.
  • There are two types of electric current known as alternating current (AC) and direct current (DC). The direct current can flow only in one direction, whereas the alternating direction flows in two directions. Direct current is seldom used as a primary energy source in industries. It mostly used in low voltage applications such as charging batteries, aircraft applications, etc. Alternating current is used to operate appliances for both household and industrial and commercial use.
  • The electric current is measured in ampere. One ampere of current represents one coulomb of electric charge moving past a specific point in one second.

1 ampere = 1 coulomb / 1 second

  • The conventional direction of an electric current is the direction in which a positive charge would move. Henceforth, the current flowing in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery.

Heating Effect of Electric Current

When our clothes are crumpled, we use the iron box to make our clothes crisp and neat. Well, you might wonder how does the iron box get hot? The heating effect of electric current is the answer to this. There are many such devices that work on the heating effect of electric current.

When an electric current flows through a conductor, heat is generated in the conductor. The heating effect of electric current depends on the following factor:

  • The time ‘t‘ for which the current flows. The longer the current flows in a conductor more heat is generated.
  • The electrical resistance of the conductor. Higher the resistance, higher the heat produced.
  • The amount of current. The larger the amount of current higher the heat produced.

The heating effect of electric current is given by the following equation

H = I2Rt

This equation is otherwise known as Joule’s equation of electrical heating.

Unit of Electric Current

The SI unit of electric current is Ampere. Ampere is defined as one coulomb of charge moving past a point in one second. If there are 6.241 x 1018 electrons flowing through our frame in one second then the electrical current flowing through it is ‘One Ampere.’

Stay tuned with Byju’s to learn more about electric current formula, Ohm’s law and much more.

Electric Current Important Questions

Q1. What is current?

Ans: Current is defined as the rate of flow of charge through the cross-sectional area.

Q2. What is conventional current?

Ans: Conventional current is defined as the flow of current from the higher potential to lower potential.

Q3. How many terminals an electric bulb consists?

Ans: 2

Q4. What is Ohm’s law?

Ans: Ohm’s law states that electric current and voltage are proportional and inversely proportional to resistance.

Q5. Why are copper wires used as connecting wires?

Ans: Because they have low resistivity.

Q6. What is the SI unit of power?

Ans: Watt

Q7. Examples of poor conductors.

Ans: Paper and tungsten.

Q8. What is the reciprocal of conductance?

Ans: Resistance is the reciprocal of conductance.

Q9. What happens to the resistance of pure metals and semiconductors with an increase in temperature?

Ans: Resistance of pure metals increases with the increase in temperature and resistance of semiconductors decreases with increase in temperature.

Q10. Name the instrument used to detect electric current.

Ans: Galvanometer.

Q11. What is the unit of charge?

Ans: Ampere-second.

Q12. What are varistors?

Ans: Varistors are the non-linear resistors.

Q13. Name the element used in the filament of an electric bulb.

Ans: Tungsten.

Q14. What is the unit of electric conductivity?

Ans: mho/metre.

Q15. Which method is used for absolute measurement of resistance?

Ans: Wheatstone bridge method is used for the absolute measurement of resistance.


Practise This Question

Pranati has set up a circuit as shown below.

Which of the following should she put in the blank box, marked 'X' to make the bulb glow more brightly?