Unit 6 – Electricity and Magnetism
NYS Standards:
4.4d Electrical energy can be produced from a variety of energy sources and can be transformed
into almost any other form of energy.
4.4e Electrical circuits provide a means of transferring electrical energy.
4.4f Without touching them, material that has been electrically charged attracts uncharged
material, and may either attract or repel other charged material.
4.4g Without direct contact, a magnet attracts certain materials and either attracts or repels other
magnets. The attractive force of a magnet is greatest at its poles.
5.2b Electric currents and magnets can exert a force on each other.
Electrical Energy
-The energy of electric charges.
Where does Electrical Energy Come From?
 4 Basic Areas
1. Dry Cell Batteries
2. Wet Cell Batteries
3. Photocells
4. Thermocouples
Where does Electrical Energy Go?
Electrical Energy can be converted to basically any
other type of energy.
o Energy can be converted to: Chemical, Heat,
Light, Electrical, Mechanical, Sound, and
Nuclear
Where does Electricity Come From?
Electricity comes from atoms.
Atoms are the smallest particle a substance can
be broken down into.
Yellow (Negative Charge, -) = Electrons
Red (Positive Charge, +) = Protons
Green (Neutral Charge, N) = Neutrons
What part of the atom is the important part?
Electrons – The negatively charged particles found
outside the nucleus.
How do electrons move from one object to another?
 2 Main Culprits
o Conductors
o Insulators
o Conductors – Materials that negative charges
move easily through. Charges are free to move
around.
 Good Conductors – Metals such as silver,
aluminum, copper, and mercury.
o Insulators – A material in which negative
charges do not move well. Found on electrical
wire to keep you from shocks.
 Good Insulators – Plastic, Rubber, Glass,
Wood, and Air.
Why do clothes stick together in the dryer?
Static Electricity – The buildup of electric charges on
an object.
o Static – Does not move.
You shocked me!
Static Discharge – When the static electricity in an
object leaves the object.
o Static Discharge is also called Electrical
Discharge.
o Examples: cracking noise, shock, and flash
of light.
Charging Objects
Where does Electrical Energy Come From?
 Electric Charge comes from all matter, but only from
specific areas of matter.
Electrons – Negative (-) Charges
Protons – Positive (+) Charges
Charges Can Exert Forces
 A charged object can exert a force – a push or pull –
on other charged objects.
Law of Electric Charges
 Like charges repel (+, + or -,-) and opposite
charges attract (+,-).
Electrical Force and Electrical Field
 Electrical Force – The force between charged objects.
o Electrical Force is Effected by Two Factors
1. Greater the charges, greater the force.
2. Distance between the charges.
Magnetic Fields like Electrical Fields?
 Just like magnetic fields, electrical fields exist around
a charged particle.
Below is an example of what an electric field would
look like.
How Do Objects Acquire a Charge?
 Objects acquire a charge three different ways.
1. Friction
2. Conduction
3. Induction
Friction
o While rubbing two objects together, electrons can be
“wiped” from one object and transferred to the other.
 As the balloon is rubbed, it loses electrons
becoming positive.
Conduction
o When electrons are transferred from one object to
another y direct contact.
 As the ruler touches the uncharged metal, its
electrons jump to the metal.
Induction
o When charges in an uncharged object are rearranged
without direct contact with a charged object.
 Remember, the charged are rearranged.
Current and Circuits
What is a Current?
 Current is the rate at which charges pass a given point
o Made by electrons moving in a wire.
AC/DC…what does that mean?
 AC/DC explains how current gets moved.
o DC - Direct Current (one direction)
o AC – Alternating Current (bi-directional)
What is a Voltage?
 Voltage is the number of electrons that are in an
energy source.
o Depends on Potential Energy
o Voltage can vary.
What is a Resistance?
 Resistance is the opposition to the flow of charge
o Expressed in ohms Ώ
o As resistance increases…current decreases.
Ohm’s Law
Amperes (A) = Volts (V)
Ohms (Ώ)
I = Current
V = Voltage
R = Resistance
I = V/R
 Current Problem Example
 What is the current flowing through a
circuit that has a voltage of 10.0 volts
and a resistance of 2.0 ohms?
I=V
R
I = 10.0 volts
2.0 ohms
I = 5.0 amps (A)
Electric Power
 The rate at which electrical energy is used to do work.
o Expressed in Watts (W )
P=VxI
Power = Voltage x Current
 Power Problem Example
 A stereo uses 5.0 amps from a source
of 120.0 volts. How much power is
used by the stereo?
P=VxI
P = 120.0 volts x 5.0 amps
P = 600.0 Watts
What are Circuits?
 Circuits are complete, closed path through which
electric charges flow.
Closed
Open
There are Two Types of Circuits
1. Series – All parts are connected in one loop.
2. Parallel – Different loads are located on separate
branches.
Magnetism
What is a Magnet?
 Magnet – Any object that attracts iron or materials
containing iron.
o Properties of Magnets
 Two Poles
 Exert Forces
 Surrounded by Magnetic Field
What are Magnetic Poles?
Every Magnet has two poles.
 Poles – The parts of a magnet where the magnetic
effects are the greatest.
North Pole
South Pole
What are Magnetic Forces?
 Magnetic Forces – The force of repulsion or attraction
between the poles of magnets.
Repulsive
Repulsive
Attractive
What is the Magnetic Field?
 Magnetic fields exist in the region around a magnet in
which magnetic forces can act.
Half a Magnet?
 What happens if you cut a magnet into pieces?
Each piece will still have two poles.
What is Electromagnetism?
 Electromagnetism is the interaction between
electricity and magnetism.
o Two Main Devices
1. Solenoid
2. Electromagnet
 Solenoids
o A coil of wire that produces a magnetic field
when carrying an electric current.
Magnetic Field
Battery
Coiled Wire
 The more loops the stronger the magnetic
field.
 Electromagnets
o Magnet that contains a solenoid wrapped around
an iron core.
Electromagnets are hundreds of times stronger due to the
combined magnetism of the solenoid and the iron core.