Electricity, Magnetism, and Electromagnetism Notes
Electricity, Magnetism, and Electromagnetism
Vocabulary
Exert: To apply or use.
Force: A push or pull.
Field: The area in which an object experiences a force that acts at a distance.
Electric Charges
Understanding electric charges is essential to understanding phenomena like receiving a shock from a doorknob.
Matter and Atoms
Everything is made up of matter.
All matter is made up of atoms.
Atoms consist of subatomic particles: protons, neutrons, and electrons.
Protons are positively charged (+).
Electrons are negatively charged (-).
Neutrons are uncharged.
Charge as a Physical Property
Charge is a physical property that an object can possess.
An object can have a positive charge, a negative charge, or no charge.
Charged objects exert a force on other charged objects.
Electric Force
Electric Force: The force of attraction or repulsion between objects due to their charges.
Like charges repel each other (+→ +, -← -).
Opposite charges attract each other (+→ -, -← +).
Factors Affecting Electric Force
The greater the charges, the greater the electric force between the objects.
The closer together the charges are, the greater the electric force between objects.
Electric Field
Electric Field: The area around a charged object in which another charged object is affected by the electric force.
The bigger the charge, the stronger and larger its electric field.
The electric field decreases as the distance from the charged object increases.
Magnets and Magnetism
Magnet: Any material that attracts iron or materials containing iron.
All magnets have two poles: a North pole and a South pole.
Magnets exert forces on each other.
Magnets are surrounded by a magnetic field.
Magnetic Poles
Each end of a magnet is called a magnetic pole.
One end of the magnet always points to the north (North pole).
The opposite end of the magnet points to the south (South pole).
Magnetic poles are always in pairs.
If a magnet is broken in half, each half gains a new pole.
Magnetic Forces
When two magnets are brought close together, they exert a magnetic force on each other.
These magnetic forces result from electrical charges in the magnets.
The force can either push the magnets apart (repel) or pull them together (attract).
Like poles repel, and opposite poles attract.
Magnetic Field
The shape of a magnetic field can be shown with lines drawn from the north pole of a magnet to the south pole.
Magnetic field lines show both the direction and the strength of a magnet's magnetic field.
The closer together the lines, the stronger the field.
The lines around a magnet are closest together at the poles, where the magnetic force is strongest.
Field lines that curve toward each other show attraction.
Field lines that curve away from each other show repulsion.
Electromagnetism
Electromagnetism: The interaction between electricity and magnetism.
It joins or unifies electric and magnetic fields into a single electromagnetic field.
Electric Currents
Electric current: The continuous flow of electric charges from one region to another.
Moving electric charges constitute an electric current.
Measurement of Electric Currents
Ammeters are devices used to measure an electric current.
They measure the rate that electric charges are moving through a wire.
The unit of this measurement is called an ampere (amp).
Compasses and Magnetic Fields
A compass is an instrument used to find North.
The needle of the compass is a small magnet.
The Earth has a large magnetic field that attracts the north side of the compass needle towards the North Pole.
When another magnet is near the needle, the needle will be affected by that magnetic field more than Earth’s magnetic field.
Electric Currents and Magnetic Fields
When an electric current is passed through a wire, the compass needle is affected and moved.
Moving electric charges generate a magnetic field.
As previously mentioned, when electric charges move, they generate a magnetic field.
Changes in the magnetic field can also affect electric charges.
Electric and magnetic forces are closely tied together and affect one another.
Magnetic fields are generated by moving electric charges.
When an electric charge is stationary, there is no magnetic field.
The magnetic field cannot be seen, but its effects can be observed with a compass.
The magnetic field that forms around a long, straight wire is in the shape of a cylinder.
Overlapping fields produce a cylindrical magnetic field around the wire, along its entire length.
Solenoids
Solenoid: A long coil of wire.
It uses loops of wires to concentrate the magnetic field into a smaller one.
The loops of wire generate a stronger, smaller magnetic field than a straight wire.
Changing the number of loops changes the strength of the magnetic field surrounding the wire.
Changing the material that the coil is wrapped around also changes the strength of the magnetic field.
Electricity, Magnetism, and Electromagnetism
Vocabulary
Exert: Apply.
Force: Push/pull.
Field: Area of force.
Electric Charges
Key to understanding shocks.
Matter and Atoms
Atoms: protons (+), electrons (-), neutrons (0).
Charge as Property
Objects: +, -, or 0 charge.
Charged objects exert force.
Electric Force
Attraction/repulsion of charges.
Like repel, opposites attract.
Factors
More charge/closer = more force.
Electric Field
Area around charge.
Large charge = strong field.
Field weakens with distance.
Magnets
Attract iron.
N and S poles.
Magnetic field.
Magnetic Poles
Magnet ends (N/S).
Always paired.
Magnetic Forces
Magnets attract/repel.
Like repel, opposites attract.
Magnetic Field
Lines show strength/direction.
Closer lines = stronger.
Electromagnetism
Electricity & magnetism interaction.