Fremont Magnet Elementary

Electricity and Magnetism Review

Standards:

1. Magnetism

Here are a few things to remind you about magnetism.
• Magnets have two poles, north and south.

• A magnet's force is strongest at the poles (the ends)

• Like poles repel

• Unlike poles attract

• Not all metals are magnetic.  It must contain iron to be magnetic.

• The Earth is like a giant magnet.  It has a north and south pole.   The Earth has an invisible magnetic field that surrounds it, just like a magnet.

This picture shows two bar magnets set down next to each other.  What will most likely happen?

Each magnet will turn from horizontal to vertical, with N up

The magnets will repel each other

The magnets will attract each other
Nothing will happen until a current is switched on

If two objects both have a negative charge what will they do?

They will attract toward each other

They will repel away from each other

They will do nothing

You can sprinkle iron filings around a magnet.  Where will the iron filings be most concentrated?

at the source of the current
at the poles
toward the magnetic switch
toward the center of the magnet

2. Electromagnets and Generators

Here are a few facts about electromagnets and generators...

• You can make a magnet using electricity - called an electromagnet

• You can make electricity using a magnet - called a generator

• There are 3 ways to change the strength of an electromagnet:

• wind wire around an iron core, like a nail

• add more winds to the coil

• increase the battery power

• Electromagnets are used in things like: fans, doorbells, washing machines, and dryers.

If a magnet is moved back and forth inside a coil wire, what will happen?

The force of the magnet becomes greater
The magnet loses its magnetic properties

The coil of wire grows very hot

The motion creates an electric current

Which of these is the main characteristic of electromagnets that makes them useful in simple tools, such as hair dryers and doorbells?

They can be very strong
They cannot transmit electricity

They can be switched on and off

They can be made of plastic

Which does not affect the strength of an electromagnet?

size of the nail in the core

amount of current from the battery

number of coils of wire

3. Circuits

Here are a few facts about circuits...

• For electricity to flow the circuit must be complete or closed.
• The flow of electricity is called current
• The current flows in 1 direction
• If you reverse current it will flow in the opposite direction.  For example, if you flip the battery the current will go the other way.
• Electrical current makes a magnetic field

 This shows some electric devices on a circuit.  On this circuit, which of the devices will work?

only the fan
the lights and the doorbell

only the light

the light, the doorbell, and the fan

The picture shows a fan spinning clockwise.  What would happen if the current changed direction?

it would spin faster
it would spin slower

it would spin in the opposite direction

it would not change

4. Converting Electricity

• Electricity can be used to heat, move, or light things. Heat Light Motion

Which of the following performs its function by converting electrical energy to motion?

electric stove
toaster

electric mixer

iron

Which of the following converts electric energy to heat and motion?

electric fan
flashlight

hair dryer

electric iron

6. Static Electricity?

Here are some things you need to know about static electricity...

• You can move electrons from one thing to another by rubbing, like shuffling your feet across the floor.
• You get shocked when you touch a doorknob because the extra electrons are pulled toward the protons in the metal.
• An unequal amount of electrons causes 2 objects to attract

• An equal amount of electrons causes 2 objects to repel

Why can you get a shock if you touch a metal doorknob after walking across a wool carpet?

You have gained electrons; the doorknob has no electrons
You have gained neutrons; the doorknob has fewer neutrons

You have lost electrons; the doorknob has many electrons

You have gained electrons; the doorknob has fewer electrons

A child rubbed two balloons with a piece of wool.  What will happen when the balloons are brought near each other?

the balloons will repel each other
the balloons will attract each other

the balloons will become positively charged

the balloons will pop

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