# What is magnetism ? Force of attraction and repulsion.

## Presentation on theme: "What is magnetism ? Force of attraction and repulsion."— Presentation transcript:

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 negative or 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 R 10 = I x 5 10/5 = 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 ? Convection Conduction Radiation

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 degrees Boiling = 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