what is magnetism ? force of attraction and repulsion
TRANSCRIPT
TEST REVIEW8th Grade Science
3/25/15
What is magnetism?
Force of attraction and repulsion
What causes magnetism?
The spin of electrons
Where is the strongest point in a magnet?
The poles
What happens to the magnetism of a wire carrying electricity if you add more coils?
It becomes stronger
What is the magnetic field?
The space around a magnet
How can we create a magnet?
• Rub a piece of iron with a magnet in one direction
• Attach a piece of iron to a magnet• Use electricity
What is the magnetosphere?
Field around the earth
How does the earth’s magnetic field help us?
Protects us from the sun
Draw the north pole next to the south pole of two magnets?
they attract one another
Where is the electric field of a charged object the strongest?
On the outside (surface) of an object
What charge does an object have if it doesn’t have enough electrons on it?
•positive
How do you make an electric field stronger?
Take away negativeor
Add positive
Draw the electric field around two positive objects?
They repel
What happens when two objects that have opposite charges come near each other?
They attract each other
What is the rule of charges?
Opposites attract,Same repel
What charge does an object have if it has too many electrons on it?
Negative
What is the electric field?
Area around a charged object
Draw the electric field around a negative object?
What happens when two objects that have the same charge come near each other?
They repel each other
How much current can be pushed through a 5 ohm resistor if the voltage is 10 volts?
V = I x R10 = I x 510/5 = 2 amps
What is the symbol for current?
What is a wet cell?
A battery that has liquid inside
What are the electrons doing an AC wire?
The electrons are going back and forth
What is the voltage in your house wiring?
120
What is current?
A flow of electrons
What is a voltage?
Push of electrons
What is resistance?
Friction to electrons moving
What are 3 ways to transfer heat?
ConvectionConductionRadiation
Give an example of heat transfer by radiation?
putting your hand by your forehead
Give an example of heat transfer by conduction?
Pan on a burner of stove
Give an example of heat transfer by convection?
Hand over a radiator
What are insulators?
Something that slows down heat transfer
What is heat?
Energy of molecules in motion
What happens to the molecules of a liquid as heat is added to it?
Molecules speed up
What are conductors?
Substances that allow electrons or heat to go through them (tend to be metal)
What happens to the molecules of a hot object if it touches a cold object?
They slow down
Why can’t we say that heat rises?
Objects rise – not energy
What units is heat measured in?
Joules and Calories
What is temperature in terms of molecules?
How fast molecules are moving
What do we use to measure temperature?
thermometer
What is the Celsius thermometer based on?
Freezing = 0 degreesBoiling = 100 degrees
What is the Kelvin thermometer based on?
The speed of molecules
Why can’t there be a temperature below zero degrees Kelvin?
Because molecules stop at zero
Why do bridges have expansion joints?
To protect from cracking in hot weather and pulling apart in cold weather
Why is it that most materials expand when heated?
Molecules move faster and further away from each other
Why does water expand when cooled to zero degrees Celsius?
Water freezes and traps space between molecules
GOOD LUCK !!!
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