Electric currents make magnetic fields

Electric currents make magnetic fields

Fill in the Blank

An electric _______ must flow through an electromagnet to make it work. The current makes a magnetic _____. ^{(write two answers separated by '/' e.g. answer a/ answer b)}

The field of an electromagnet

• The magnetic field of an electromagnet is just like the magnetic field of a bar magnet

• Magnetic field lines come out of one end of the magnet (its north pole)

• The magnetic field lines go back in the other end of the magnet (its south pole)

Current and field

• Hans Christian Oersted was a Danish Scientist (from Denmark)

• He thought that there was a connection between electricity and magnetism

• One day, in 1820, he was giving a lecture about electric circuits. A compass was lying nearby on a table. When he switched on the circuit he noticed the compass's needle changing...

Multiple Select

Which of these countries is Denmark?

• A

• B

• C

• D

Current and field

• Oersted discovered that whenever an electric current flows in a wire, it makes a magnetic field around it. ^{This photo shows a modern version of the experiment}

• When the switch is closed, the battery makes a current flow in the wire . The compass needle moves around, just like Oersted's experiment

How an electromagnet works

• The magnetic field around the wire is quite weak

• An electromagnet is a clever idea that works because when you wind the wire into a coil, you concentrate the magnetic field into a smaller space, making it much stronger

Multiple Choice

How would increasing the number of coils of wire around the bar affect the electromagnet?

• It would make the poles of the magnet weaker.

• It would make the poles of the magnet stronger.

• It would decrease the flow of electricity in the iron bar.

Multiple Choice

Which of these best describes a magnetic field?

• a measure of the length of a magnet

• the force that pushes two magnets away from each other

• a region around a magnet in which magnetic forces can be measured

Multiple Choice

Moving two magnetic objects closer together will __________________ the strength of the magnetic force between them.

• decreases

• increases

• not change

Multiple Choice

What relationship is shown between the two magnets interacting with iron filings.

• Electric force between LIKE charges is attractive.

• Magnetic force between LIKE poles is attractive

• Electric force between OPPOSITE charges is attractive.

• Magnetic force between OPPOSITE poles is attractive.

Multiple Choice

When using a compass to investigate magnetic forces. Which of these will cause the compass to change direction?

• plastic paper clips

• a wooden doorknob

• the wire he is using to charge a cell phone

• a copper penny

Multiple Choice

what are the Main parts of an electric circuit

• a source of energy and a potato

• E=mc2

• a switch with a connecting wires

• source of energy, conducting wires, and usually, a switch

Multiple Choice

what is an electric current

• something that conducts energy

• part of a light bulb

• the flow of electric charge

• lightning

Multiple Choice

was Hans Christian Oersted...

• the guy in frozen

• danish physicist

• German physicist

• the guy who created magnets

Multiple Choice

If the current in the wire increases, what happens to the strength of the magnetic field?

• It decreases

• It increases

• It stops the magnetic field

• No change