Physics Exam

Magnets

Do you specialize in magnetism? Because you’ve got a powerful pull.

• Magnets have a NORTH and SOUTH pole

• Magnetism flows in an invisible magnetic field

• The flow always goes from the NORTH POLE to the SOUTH POLE

North/South poles & magnetic field lines.

• MAGNETISM is the force exerted by magnets when they attract or repel each other:

  • opposites attract (pull)

  • the same poles repel (push)

North/South poles & magnetic field lines.

• You get two smaller magnets with a north and south pole each!

• Maybe a monopole is possible (only North poles or only South poles) but no one has seen one!

What happens when you break a magnet?

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​N

​N

​N

​S

​S

​S

Why are some things Magnetic?

• Everything is made up of atoms

• Atoms have small electrons flying around them

• Electrons have an electro-magnetic charge

Why are some things Magnetic?

• If electrons all SPIN IN DIFFERENT directions then their charges cancel each other out and there is no magnet
  ---------------------------------------------------

• If electrons all SPIN IN THE SAME direction then you get a unified charge and you get a magnet

Why are some things Magnetic?

• Rubbing a metal with a magnet can make the electrons line up the same way and make the metal a magnet!

  • This can also sometimes be done with an electrical current (electromagnetism)

Electromagnetism

• Electric currents/ Electricity is made up of electrons moving in the SAME DIRECTION

  • this can create a magnetic field around metals like iron

• Magnets made from a current-carrying wires are called ELECTROMAGNETS

• Electromagnet made from a coil of wire is a SOLENOID

• When a current goes through it, the magnetic field of a solenoid is the same as a bar magnet

A CURRENT going through a WIRE causes a magnetic field around it

• When you turn the electricity off, the magnetic field can be turned off as well!

A CURRENT going through a WIRE causes a magnetic field around it

Multiple Choice

What is the coil of wire called?

• A current

• Electromagnetism

• Solenoid

• Conductor

Multiple Select

What are the ways to make metals magnetic?

• Rub a metal with a magnet

• Run an electric current through it

• All metals are normally magnetic

• Attach it to a needle

Multiple Select

What happens when electrons spin in different directions?

• Unmagnetized

• Magnetized

• Their charges cancel each other out

• Their charges become unified

Multiple Select

What happens when electrons spin in the same direction?

• Unmagnetized

• Magnetized

• Their charges cancel each other out

• Their charges become unified

Multiple Choice

what kind of charge do electrons have?

• negative

• positive

• neutral

• electric

Fill in the Blanks

To increase the strength of an electromagnet, you can put more turns on the

.

Multiple Choice

What happens if you use a steel core instead of a soft iron core?

• The electric current gets stronger and way too powerful for the solenoid to handle

• It stays magnetized even after the current is turned off

• It forces the electrons to spin in opposite directions which demagnetizes the current

• It acts like a battery to the soft iron core.

1. Know about north/south poles and magnetic field lines.
2. Know which parts of the magnet attract and repel.
3. Know what you get when you break a magnet in half.
4. Know what the spin of an electron has to do with magnets

​REVIEW: Basics

Multiple Choice

What happens when you break a magnet in two?

• A magnet with monopoles

• A magnet with only North Poles

• Magnets with two north poles and two south poles each

• Two smaller magnets

1. Explain how you can make a magnet using a battery.
2. Explain how you could make that magnet stronger (3 ways)

​REVIEW: Electromagnetism

• Hard drives have spinning disks that store information and a head that reads/writes information

  • magnetic sensor on the head "reads" the code

  • the electromagnet on the head "writes" the code
    

Hard drives

• The head uses an electromagnet to write a magnetic code on the disk

• The head changes some parts of the disk to NORTH and others to SOUTH (known as 1 and 0)
  

Hard drives

1. Be able to explain how a hard drive/Festplatte works.

​REVIEW: Computer Memory

​Confusing fact: the MAGNETIC south pole is located in the geographic NORTH pole and vice versa! Remember, magnetic fields always move from North to South.

The needle on the compass is magnetized.

The magnetic south part of the needle lines up with the magnetic north part of the Earth. The opposite poles attract.

• Solar wind from the Sun is made up of particles that have protons (+) and electrons (-)

Solar Wind

• The magnetic field around the earth pushes the solar wind away

• SOME particles do get in through the poles and light up the sky

• Known as AURORA BOREALIS

Solar Wind

Aurora Borealis

• ​When the particles hit oxygen it turns into green lights

• When the particles hit nitrogen, it turns into blue and purple light

• Mars used to have a magnetic field, but it disappeared

• Without any protection, the solar wind blew the atmosphere away

• With no way to trap the heat, the water froze

Mars

1. Know how a compass works and what that has to do with the core of the Earth.
2. Know how the Earth’s magnetism protects us from the Sun.
3. Know what causes aurora borealis.
4. Know what happened to Mars after it lost its magnetic field.

​REVIEW: Planetary Magnetism