【学习笔记】懂你英语 核心课 Level 5 Unit 3 Part 4（I）听力 Electromagnetic Force

are several fundamental forces that hold our universe together.

One of these, of course, is gravity, the force between objects that have mass.

Another important force is the electromagnetic force.【跟读】

The electromagnetic force is responsible for chemical reactions.

Without it there would be no atoms or molecules.

Up until a couple of hundred years ago, very little was known about this force.【填空】

Learning about the electromagnetic force and how to use it was a major step forward.

It revolutionized communication, transportation and manufacturing.

Imagine what life would be like without electricity!

【选择】-Which of the fundamental forces is between objects that have mass?   -Gravity.

The electromagnetic force has two parts, the electric force and the magnetic force.

The electric force is the force between electrically charged particles such as electrons and protons.

Electric charges attract or repel each other with a force that depends on the distance between them.

The magnetic force is the force between magnetic poles, such as the north and south pole.

In fact, the Earth is like a large bar magnet, with a north and a south pole.【跟读】

Many animals use the Earth's magnetic field to navigate during their migrations.【填空】

We can also see this magnetic field when we use a compass.

【选择】-For what purpose do many animals use the Earth's magnetic field?    -for navigation.

【选择】-Electrons and protons are examples of what?    -electrically charged particles.

Why does the Earth have a magnetic field?

Many scientists believe that the Earth's magnetic field is due to the Earth's rotation.

Deep inside the Earth is a solid iron core, surrounded by a liquid metal outer core.

The moving electric currents inside this liquid metal create a magnetic field.

【选择】-What's deep inside the Earth?   -a solid iron core.

The Earth's magnetic field is important because it protects us from the solar wind.

The solar wind is a current of charged particles coming at us from the Sun.

When the solar wind nears the Earth, the Earth's magnetic field deflects it away.

This protects the Earth from the radiation, which can be dangerous to life.【填空】【跟读】

It also protects the satellites that we use for communication.

【选择】-What protects the Earth from the solar wind?   -The Earth's magnetic field.

【选择】-How does the magnetic field protect the earth?   -If deflects the solar wind away from the Earth.

【选择】-When the solar wind nears the Earth, the Earth's magnetic field deflects if away.     -This is the Earth from the radiation, which can be dangerous to life.

【跟读】The Earth's magnetic field is important because it protects us from the solar wind.

【跟读】The Earth's magnetic field protects the Earth from the solar wind.

【跟读】Many scientists believe that the Earth's magnetic field is due to the Earth's rotation.

【跟读】When the solar wind nears the Earth, the Earth's magnetic field deflects it away.