Electricity and Magnetism. Natural Science unit 5

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Hans Christian Oersted discovered the connection between electricity and magnetism in 1820. He saw that his compass was aﬀected when an electric current was switched on and oﬀ nearby.

André-Marie Ampere investigated the relationship between electricity and magnetism. One of his discoveries was the electron, which creates both magnetism and electricity.

Michael Faraday He showed that by moving a loop of wire over a magnet, an electric current was produced in the wire. His experiments proved that a changing magnetic ﬁeld produces an electric ﬁeld. He called this invention the ’electromagnetic rotary device’. This invention was the basis for the ﬁrst electric motor, or dynamo. Modern electrical generators are still based on this principle.

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If you held a north end to a south end of a magnet, would they attract?

Is the north end of a magnet positively or negatively charged?

The north pole of a magnet is positively charged; the south pole is negatively charged.

Speakers and microphones In a speaker, electric current causes a cone to vibrate and produce sound. A coil is attached to the cone.

In a microphone, sound waves cause the cone to vibrate. The vibration is then transformed into an electric current as the coil moves through the magnetic ﬁeld of a magnet.

What is the center of the Earth made of?

What would happen without the magnetosphere?

Maglev A magnetic levitation train, or maglev, uses electromagnets to levitate above its track. Magnets are also used to move the train forward. Maglevs can travel at very high speeds because there is no friction between the train and the track.

Magnets and electricity are used all around us! Can you think of more ways you use magnets and electricity?

source: New Think Do Learn. Natural Sciences 6. Madrid Edition. Oxford Education

Electromagnets are made from a wire coiled around an iron rod. The wire is then connected to a power source, such as a battery. When the circuit is complete, electric current ﬂows along the wire and a magnetic ﬁeld is generated. Electromagnets produce a magnetic ﬁeld when electric current is ﬂowing through the wire. But when the electric current is switched oﬀ, the magnetic ﬁeld disappears. So an electromagnet creates a magnetic ﬁeld that can be switched on and oﬀ.

Keep reading to find the many uses of electromagnets!

What is Magnetism? It's an invisible force between two magnetic objects or between a magnetic object and an object made of magnetic materials (like iron).

Like electricity, magnetism is created by electrons. How does an object become magnetic? The electrons in the atoms that make up the object must orbit the nucleus in a specific direction. So the direction of the orbit of the electrons determines if a substance is magnetic or not!

Bar magnets are permanent magents. This means they can't be switched on and off: they always have a magnetic field. They have 2 poles: North and South. North pole = positively charged south pole = negatively charged

Electrons can move to another atom, and when we force an electron to leave its atom and begin orbiting a different atom, the balance between positive and negative charges in each atom changes. 

The constant movement of electrons between atoms is called electric current. The atom that has gained an electron now has more negative electrons than positive protons. This imbalance between the charges attracts an electron from another atom. When an electron is pulled away from its orbit, it leaves an unbalanced atom, which pulls another electron away from its orbit, and so on.

Which part of the atom is responsible for creating an electric current?

Electrons. The constant movement of electrons between atoms is called the electric current

What components can you find in an electric circuit?

Battery, wire, light bulb, switch off, switch on.

Electricity is the movement of electrons from one atom to another. In order to produce electricity, a force is needed to make an electron leave its orbit.

Remember: electrons are particles that orbit the nucleus. Electrons have a negative charge.

In a microphone, what causes the cone to vibrate?

What are electromagnets made from?

We can generate electricity with magnets. In power stations, where the electricity we use in our homes, schools and oﬃces is generated, huge generators containing magnets are used to produce electric current. As water or gas moves past a turbine, the turbine turns. This moves a magnet around a coil of wires which produces electric current in the wires.

the outer layers of the atmosphere would be damaged by solar radiation

We can usually find the following components in an electric circuit: Light bulb, switch, battery, and a wire.

Where is the electricity stored? The Battery Where does the electricity flow? The conductor. The conductor is wires made from metals, like copper.

A circuit is a continuous circle from the battery, through the components and back to the battery. When electric current is flowing, the lamp lights up. A switch in a circuit can turn the current on and off.

The magnetosphere is the Earth’s magnetic ﬁeld. A north pole is the end of a magnet which points north when suspended freely. The magnetosphere protects life on Earth by deﬂecting solar radiation.

The magnetosphere extends from the South Pole to the North Pole. If we could draw this magnetic ﬁeld, the Earth would look like it had a bar magnet in its centre. The magnetosphere extends all around the Earth and into the atmosphere around it. However, the North Pole is actually the south pole of the Earth’s magnetosphere.

What causes the magnetosphere? The centre of the Earth is made of liquid iron. Because it’s liquid, it moves slowly as the Earth rotates on its axis. This movement causes a magnetic ﬁeld to form around the whole planet.

Why is the magnetosphere important? The magnetosphere is essential to life on Earth because it deﬂects solar radiation from the Sun back out into space. Without the magnetosphere, the outer layers of the atmosphere would be damaged by solar radiation. As a result, dangerous radiation would reach the surface of the Earth. Radiation is harmful for plant and animal life on Earth, so many species would quickly become extinct.

The magnetosphere also helps us to navigate. By using a compass, we can always see which direction is north wherever we are. A compass has a magnetised steel needle that is balanced inside a container. The north pole of the needle is painted red. The needle moves horizontally around a ﬁxed point inside the container. The north pole of the needle is attracted to the magnetic north pole of the Earth, which is actually the south pole of the magnetosphere. As a result, as we travel from one place to another, the red end of the needle will always point north.

What did Faraday invent?

’electromagnetic rotary device’, known as the Dynamo

Electric current produces a magnetic ﬁeld when it ﬂows along a...

Electricity and magnetism are related. The study of how electricity and magnetism are related and how they interact with each other is called electromagnetism.

Electric current produces a magnetic ﬁeld when it ﬂows along a wire. A magnet can also create electric current in a wire. To create an electric current, we can move a magnet in a circular motion around a coil of wire. This changing magnetic ﬁeld causes the electrons in the wire to begin to jump from their orbits. As we have seen before, when electrons jump from the orbit of one nucleus to that of another, electric current is produced.

What does a magnetic ﬁeld look like? We can see the magnetic ﬁeld of a bar magnet using iron ﬁlings. When the iron ﬁlings are sprinkled over and around the magnet, they form lines.The lines of ﬁlings indicate the location and direction of the magnetic ﬁeld.

These magnets are attracting each other. Look at the curved lines at the poles that extend from one magnet to the other. These lines represent the attraction between the two magnets. These magnets are repelling each other. Look at the lines at the poles. They don’t join up; they turn away from each other. They repel each other.

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