Chapter 8

Electricity and Magnetism

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

Introduction

Let us begin with the introduction to electricity. In simple words, you can understand electricity as the presence and movement of charged particles. It is imperative to start understanding the basic electricity principles to help you answer your queries. The first step to understand the electricity concept is with the nature of matter. We have already studied that matter is made up of molecules, which are made up of atoms. Atoms are further composed of neutrons, protons, and electrons. Electricity can be dynamic or static. The two differ based on whether the electrons are in motion or at rest.

In simple words, an electric current means the flow of charge. Charge carriers or moving electrons carry this charge in a wire. When we talk about current, we mean the movement of electrons to the positive battery terminal from the negative battery terminal through the circuit. The electric current is related to the resistance and voltage of the circuit.

Various instruments are used to measure electric currents. Here are a few-

  • Galvanometer- It is an instrument that measures a function of the current or a small electrical current by deflection of a moving coil. Detection Of Current By Galvanometer also measures the magnitude and direction of the current.
  • Ammeter- It is another instrument that is used to measure the current in a circuit. The SI Unit of measuring current is amperes.  The Detection Of Current By Ammeter measures the magnitude of the current.

When discussing electric current, we also come across the concept of direct current. It can be defined as the unidirectional flow of current or electric charge. There are various sources of direct current. These are semiconductors, conductors like wire, and even through the vacuum. The rate of flow of charge is referred to as electric current. Ampere is the SI unit for measuring the rate of electric charge flow. It is equal to a charge that flows through the same surface at one coulomb per second.  

  • Conductors- Conductors are elements that allow the quick flow of electric charge. Thus, elements like copper, silver, and gold are good conductors, as they contain many free electrons. The atoms in these elements have electrons that are loosely bound in their outer orbits. These electrons break loose from the outer orbit and drift freely through the material. There is only one electron in the outer orbits of silver and copper elements, and there will be billions of free electrons in a piece of silver wire at room temperature.
  • Insulators-  As the name suggests, insulators are materials that do not allow the electric charge flow. Examples of insulators are plastic, ceramic, and glass. Normally, atoms in these materials have no free electrons, which impedes electric current flow through them. Only if the material has a high and strong electric field does its outer electrons get dislodged.
  • Semiconductors- These materials fall in between insulators and conductors. Some examples of semiconductors are germanium and silicon.

The direction of current is the direction in which the positive charge moves. Thus, the external circuit current moves away from the positive terminal towards the battery’s negative terminal.

Magnetism is defined as the characteristic of the collective electromagnetic force. It is related to particular phenomena occurring from the magnetic force. Magnetic fields are created by objects that attract or repel other objects.

The Earth’s Magnetic Field is also referred to as the geomagnetic field. The Earth also has a magnetic field that covers millions of kilometres into outer space. The planet looks like a bar magnet, with its south magnetic pole near the North Pole, and the magnetic North Pole is close to Antarctica. Although the Earth’s magnetic field extends to a great distance, it is weak in terms of magnetic field strength. The rotation of our planet on its axis results in electric currents forming a magnetic field extending around the planet.

The theory of the Dynamo effect explains the cause of Earth’s magnetism. As per this theory, the planet gets its own magnetic field lines due to the presence of metallic fluids present in its inner and outer core. Molten iron is present in the outer core, while solidified elements are present in the inner core. Nickel and molten iron present in the inner core create convection currents responsible for the generation of Earth’s magnetism. These currents have charged particles that generate magnetic fields.

In conclusion, this chapter discusses electricity and magnetism in detail. Both electricity and magnetism are important concepts in physics. An electric current means the flow of charge, whereas magnetism is defined as the characteristic of the collective electromagnetic force.

  1. How does Induced Magnetism by bar magnet work?
    The induced magnetism by Bar Magnet works and becomes a magnet only when it is positioned in a magnetic field. As soon as it is removed from the magnetic field, it loses its magnetism.
  2. What is a Magnetic Compass?
    The instrument used to determine direction on the Earth’s surface using a magnetic pointer that aligns itself with the magnetic field of the Earth is known as the Magnetic Compass. It is a popular surveying or navigational instrument.
  3. What are Lines of Ma?
    The lines of Ma are the field lines that indicate the direction pointed by a small compass when placed at a location.
  4. What are conductors? Give a few examples.
    Conductors are elements that allow the quick flow of electric charge. Thus, elements like copper, silver, and gold are good conductors, as they contain many free electrons.

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