Electricity and magnetism

Most of us rely on electricity in almost every minute of our life. Electricity is used to describe electric energy.

Electric energy begins with charged particles.

Electric energy is the basic property of matter. All matter is made up of tiny building blocks called atoms. Atoms are composed of smaller particles called protons, neutrons, and electrons.

The protons carry a positive charge (+), an electron has a negative charge (-). A neutron has no charge. Protons and neutrons make up the nucleus of an atom. Electrons move quickly around the nucleus.

When the number of electrons in an atom is equal to protons, the atom has a charge of zero. When the number of electrons and protons in an atom are not equal, the atom has a positive or negative charge.

STATIC CHARGE

Most of the time, materials or objects are electrically neutral.

  • If a neutral object gains electrons, the object will have more negative charges than the positive charges. This excess of negative charge causes the object to be negatively charged.

  • If a neutral object loses electrons, the object will have an excess of positive charge. The object will be positively charged.

  • The object's excess of positive or negative charge is called static charge This buildup of charge on an object is known as static electricity as it does not move from one place to another.

These two kinds of electrical charge, positive or negative, can:

  • repel (push away) each other-if they are the same kind of charge

  • attract (pull toward) each other, if they are opposite charges.

Rubbing materials together produces static electricity, because it gives the materials an electric charge.

When two objects touch or nearly touch, charged particles can move from one object to the other.

Negative charges move from object to object more easily than positive charges.

For example, when you rub a balloon against your hair:

  • negative charges move from the hair to the balloon.

  • the balloon now has more negative charges than positive charges.

The balloon is negatively charged.

When a negatively charged balloon comes in contact with a wall, it sticks to the wall making it positively charged.

When we rub a plastic ruler with a piece of cloth, the ruler pulls electrons from the cloth. This gives it a negative charge.

The cloth becomes positively charged because it has lost electrons.

If you rub a comb on your sleeve, you can use it to pick up little pieces of paper.

The comb picks up the paper because of static electricity

ELECTRIC CURRENT

When you plug in a TV set and turn it on, electric charges are flowing through wires. A flow of electric charges is an electric current. In an electric current, electric charges keep moving until you turn the current off.

Electric current can flow through many materials, but most materials limit the flow of current.

A conductor is a material that lets charges flow through it easily

Metals such as copper and silver are good conductors. Even a person can be a conductor That's why you can get a shock when another person touches you

An insulator is a material that does not let charges flow through it easily

When you touch a wooden door, charges move slowly onto the door. You don't feel a shock.

Other insulators are:

  • glass

  • rubber

  • plastic

ELECTRIC CIRCUITS

An electric circuit is a path for electric current. It has three main parts:

  • A conducting path

The wire is one of the conducting paths, it links the source of charge and the device in a loop. In homes, the wire is made of copper surrounded by plastic coating.

  • A source of electric energy

A battery is a source of electric energy. A battery converts chemical energy to electric energy.

  • A device that uses electricity to work such as bulb, a lamp, or a computer

Electricity flows through a circuit when everything is joined up correctly This electricity is called current. The current flows from the power source, which produces the electricity, through conductors, and back to the power source. This is why it is called a circuit. Current flows from positive to negative terminal of the power source

MAGNETS

A magnet is a material which attracts the metals like iron. cobalt, and nickel. Magnets create an invisible magnetic force.

Electricity and magnetism are closely related. When an electric current flows through a wire, a magnetic field is created around the wire.

Although magnets may have different shapes, sizes, and strength, all magnets have two magnetic ends called poles.

  • a North Pole

  • a South Pole

The force of the magnet is strongest at the pole.

Just like electric charges, unlike poles attract each other and like poles repel each other.

EARTH AS A MAGNET

The Earth behaves as a giant magnet. At the centre of the Earth is a liquid core. The core is made up of molten metals that are magnetic. It creates a huge magnetic pulling force.

The north pole of Earth's magnetic field is located near the geographic North Pole Earth's magnetic south pole is located near the geographic South Pole.

The North end of a bar magnet is attracted to North pole. The south end of a bar magnet is attracted to the South pole.

If you hang a bar magnet with a string, it will swing around until North end points to North pole of Earth and South end points towards South pole of the Earth.

1. Hang a bar magnet by a string.

2 Allow it to hang freely and observe it.

3. You will note that the magnet orients itself such that its north pole points towards the Earth's north pole and it's south pole towards the Earth's south pole.

Compass

A compass is a small instrument that helps us to find directions.

A compass has a needle which is small, thin magnet. It can move freely so its North end is attracted to Earth's north magnetic pole. It always lies in North to South directions.

Ships, aeroplanes and explorers use it to find the way.

TYPES OF MAGNETS

There are three types of magnets. Permanent magnets retain their magnetic properties and exhibit magnetic behaviour for a long period of time. Temporary magnets act like magnets when exposed to a strong magnetic field. We can create temporary magnets by stroking a piece of iron or steel (e.g. a needle) along a permanent magnet. And lastly, electromagnets, are a type of temporary magnet created by the flow of electric current through it.

ELECTROMAGNETS

An electromagnet is a magnet that can be switched on and off with electricity When the current flows it works like a magnet. when the current stops, it goes back to being an ordinary metal.

Electromagnet shows that electricity can produce magnetism. When an electric current passes through a wire, a magnetic field is set up around the wire.

If a small compass is placed near the wire carrying a current, the compass needle moves due to the magnetic field around the wire.

Facts

  • Like poles repel each other, while unlike poles attract.

  • Magnets come in many shapes-bar, circles, and this horseshoe shape. They attract metallic paper clips, but no plastic paper clips.

  • Many circuits also have a switch to turn the electric current on or off

  • The wires are conductors. The plastic wrapping is an insulator that protects you from the electricity in the wire.

  • A light bulb converts electric energy into light.

  • Because a compass needle points north, the compass can be used to find all the other directions as well.