Electricity
Magnetism, Electricity & Electromagnetism
Ms. Mannix
2016 Honors Physical Science
DFA
Electricity - What Is Magnetism?
Magnetic Fields
Magnetic field lines spread out from one pole, curve around
the magnet, and return to the other pole.
Electricity - What Is Magnetism?
Magnetic Fields
When the magnetic fields of two or more magnets overlap,
the result is a combined field.
Electricity - What Is Magnetism?
Magnetic Field Lines Activity
Click the Active Art button to open a browser window and
access Active Art about magnetic field lines.
Electricity - Inside a Magnet
The Atom
An atom contains neutrons and positively charged protons in
its nucleus. Negatively charged electrons move randomly
throughout an atom.
Electricity - Inside a Magnet
Magnetic Domains
In a magnetized material, all or most of the magnet domains
are arranged in the same direction.
Electricity - Inside a Magnet
Magnetic Domains
Modern magnets come in a variety of shapes
and are made from many different materials.
Electricity - Inside a Magnet
Making and Changing Magnets
Each piece of a magnet retains its magnetic properties after
it is cut in half.
Electricity - Magnetic Earth
Earth as a Magnet
Just like a bar magnet,
Earth has a magnetic field
surrounding it and two
magnetic poles.
Electricity - Magnetic Earth
Movement of Earth’s Magnetic Poles
Earth’s magnetic poles move
slowly over time. The data in the
table show the position of
Earth’s magnetic north pole in
specific years.
Electricity - Magnetic Earth
Movement of Earth’s Magnetic Poles
Interpreting Data:
What is the trend in the speed
of the pole’s movement?
The average speed of the
pole’s movement is
increasing.
Electricity - Magnetic Earth
Movement of Earth’s Magnetic Poles
Calculating:
What is the total distance the
pole has traveled over the
time shown?
Between 1948 and 2001, the
pole has moved 857 km (150
km + 120 km +120 km + 180
km + 287 km).
Electricity - Magnetic Earth
Movement of Earth’s Magnetic Poles
Predicting:
Using the data, predict the
average speed of the pole’s
movement between 2001 and
2010. Explain.
The average speed increased by
23 km/yr from 1994 to 2001.
That is an increase of 3.3 km/yr
per year. There are 9 years
between 2001 and 2010.
Therefore, a good prediction is
that the average speed in 2010
will be 29.7 km/yr.
Electricity - Magnetic Earth
The Magnetosphere
The solar wind causes Earth’s magnetic field to stretch out
on the side of Earth not facing the sun.
Electricity
Electricity
Electricity - Electric Charge and Static Electricity
Electric Charge
Charges that are the same repel each other. Charges that
are different attract each other.
Electricity - Electric Charge and Static Electricity
Electric Force
An electric field is a region around a charged object where
the object’s electric force is exerted on other charged objects.
Electricity - Electric Charge and Static Electricity
Electric Force
An electric field is a region around a charged object where
the object’s electric force is exerted on other charged objects.
Electricity - Electric Charge and Static Electricity
Transferring Charge
There are three methods by
which charges can be
transferred to build up static
electricity: charging by friction,
by conduction, and by induction.
Electricity - Electric Charge and Static Electricity
Transferring Charge
An electroscope can be used to detect the presence of a
charge.
Electricity - Electric Current
Flow of Electric Charges
Electric current is the continuous flow of electric charges
through a material.
Electricity - Electric Current
An Electric Circuit
An electric circuit is a complete, unbroken path through
which electric charges can flow.
Electricity - Electric Current
Resistance
Two factors that affect the resistance of water flowing in a
pipe are diameter and length. The diameter and length of a
wire also affect resistance in a circuit.
Electricity - Batteries
The First Battery
Volta built the first
electric battery by
layering zinc, paper
soaked in salt water,
and silver.
Electricity - Batteries
Electrochemical Cells
An electrochemical cell is a device that transforms chemical
energy into electrical energy.
Electricity - Batteries
Electrochemical Cells
An electrochemical cell in which the electrolyte is a liquid is a
wet cell.
Electricity - Batteries
Electrochemical Cells
A dry cell is an electrochemical cell in which the electrolyte is
a paste.
Electricity - Electric Circuits
Features of a Circuit
Simple symbols are used to diagram a circuit.
Electricity - Electric Circuits
Series Circuits
In a series circuit, there is only one path for the current to
take.
Electricity - Electric Circuits
Parallel Circuits
In a parallel circuit, there are several paths for the current to
take.
Electricity - Electric Circuits
Decimals
When calculating voltage, you often use decimals. When
you multiply two decimals, the number of decimal places in
the product is the sum of the number of decimal places in
each decimal you multiply.
If a circuit has a resistance of 30.5 ohms and a current of
0.05 amps, what is its voltage?
Electricity - Electric Circuits
Decimals
Practice Problem
Use Ohm’s law to calculate the voltage of a circuit with a
resistance of 15.2 ohms and a current of 0.10 amps.
1.52 volts
Electricity - Electric Circuits
Calculating Resistance
The brake light on an automobile is connected to a 12-volt battery.
If the resulting current is 0.40 amps, what is the resistance of the
brake light?
Read and Understand
What information are you given?
Battery Voltage = 12 V
Current = 0.40 A
Electricity - Electric Circuits
Calculating Resistance
The brake light on an automobile is connected to a 12 volt battery.
If the resulting current is 0.40 amps, what is the resistance of the
break light?
Plan and Solve
What quantity are you trying to calculate?
The resistance of the brake light
What formula contains the given quantities and the unknown
quantity?
Resistance = Voltage/Current
Perform the calculation.
Resistance = 12 V/0.40 A = 30 Ω
Electricity - Electric Circuits
Calculating Resistance
The brake light on an automobile is connected to a 12-volt battery.
If the resulting current is 0.40 amps, what is the resistance of the
brake light?
Look Back and Check
Does your answer make sense?
The answer makes sense because you are dividing the voltage by
a decimal. The answer should be greater than either number in the
fraction, which it is.
Electricity - Electric Circuits
Calculating Resistance
Practice Problem
In a circuit, there is a 0.5-A current in the bulb. The
voltage across the bulb is 4.0 V. What is the bulb’s
resistance?
8.0 Ω (4.0 V ÷ 0.5 A)
Electricity - Electric Circuits
Calculating Resistance
Practice Problem
A waffle iron has a 12-A current. If the resistance of the
coils is 10 Ω, what must the voltage be?
120 V (12 A X 10 Ω)
Electricity - Electric Power
Electric Power
The rate at which energy is transformed from one form to
another is known as power. Power is measured in watts (W).
Electricity - Electric Power
Calculating Power
A household light bulb has about 0.5 amps of current in it. Since
the standard household voltage is 120 volts, what is the power
rating for this bulb?
Read and Understand
What information have you been given?
Current = 0.5 A
Voltage = 120 V
Electricity - Electric Power
Calculating Power
A household light bulb has about 0.5 amps of current in it. Since
the standard household voltage is 120 volts, what is the power
rating for this bulb?
Plan and Solve
What quantity are you trying to calculate?
The power of the light bulb = ?
What formula contains the given quantities and the unknown
quantity?
Power = Voltage X Current
Perform the calculation.
Power = 120 V X 0.5 A
Power = 60 W
Electricity - Electric Power
Calculating Power
A household light bulb has about 0.5 amps of current in it. Since
the standard household voltage is 120 volts, what is the power
rating for this bulb?
Look Back and Check
Does your answer make sense?
The answer is reasonable, because 60 W is a common rating for
household light bulbs.
Electricity - Electric Power
Calculating Power
Practice Problem
A flashlight bulb uses two 1.5-V batteries in series to
create a current of 0.5 A. What is the power rating of the
bulb?
1.5 W (3.0 V X 0.5 A)
Electricity - Electric Power
Calculating Power
Practice Problem
A hair dryer has a power rating of 1,200 W and uses a
standard voltage of 120 V. What is the current through
the hair dryer?
10 A (1,200 W ÷ 120 V)
Electricity
Calculating Electrical Energy
E=Pt
Electricity - Electrical Safety
Electrical Equipment and Fires
If electrical equipment is not
properly used and maintained, it
can cause fires. The circle graph
shows the percentage of fires
caused by different types of
electrical equipment.
Electricity - Electrical Safety
Electrical Equipment and Fires
Reading Graphs:
What determines the size of
each wedge in the graph?
The percentage of fires
caused by a certain type of
electrical equipment
Electricity - Electrical Safety
Electrical Equipment and Fires
Reading Graphs:
What percentage of fires are
caused by appliances?
15%
Electricity - Electrical Safety
Electrical Equipment and Fires
Interpreting Data:
Which category of equipment
is responsible for the most
fires? Which category is
responsible for the fewest
fires?
Cooking equipment is
responsible for the most fires.
Heating and cooling
equipment is responsible for
the fewest fires.
Electricity - Electrical Safety
Grounding
One way to protect people from
electric shock and other electrical
danger is to provide an alternate
path for electric current.
Electricity - Electrical Safety
Breaking a Circuit
In order to prevent circuits from overheating, devices called
fuses and circuit breakers are added to circuits.
Electricity
Graphic Organizer
Devices to prevent circuits
from overheating
include
Fuses
Circuit
breakers
work by
work by
Melting
Bending
away from
wires
Electricity
- What Is Electromagnetism?
Electric Current and Magnetism
An electric current produces a magnetic field.
Electricity
- What Is Electromagnetism?
Solenoids
The magnetic field produced by a current has three distinct
characteristics. The field can be turned on or off, have its
direction reversed, or have its strength changed.
A solenoid is a type of electromagnet when the purpose is
to generate a controlled magnetic field.
Electricity
- What Is Electromagnetism?
Solenoids
The magnetic field around a solenoid resembles that of a bar
magnet.
Electricity
- What Is Electromagnetism?
Electromagnets
A doorbell rings as the magnetic field of an electromagnet
turns on and off.
Electricity
- What Is Electromagnetism?
Electromagnets
Electromagnets are used to lift heavy objects. A switch is
turned on in the crane so that a current is produced in the
electromagnet.
Electricity
Electricity, Magnetism,
and Motion
Electrical Energy and Motion
When a wire with current is placed in a magnetic field,
electrical energy is transformed into mechanical energy.
Electricity
Electricity, Magnetism,
and Motion
Galvanometers
An electric current is used to turn the pointer of a
galvanometer.
Electricity
Electricity, Magnetism,
and Motion
Electric Motors
An electric motor transforms electrical energy into
mechanical energy.
Electricity
- Electricity From Magnetism
Induction of Electric Current
An electric current is induced in a conductor when the
conductor moves through a magnetic field.
Electricity
- Electricity From Magnetism
Induction of Electric Current
If a magnet moves through a coil of wire, a current is induced
in the wire.
Electricity
- Electricity From Magnetism
Generators
A generator uses motion in a magnetic field to produce an
electric current.
Electricity
- Electricity From Magnetism
Generators
In most generators, a source of mechanical energy turns
huge turbines such as this one. The turbine is attached to the
armature of a generator, which produces current.
Electricity
Compare and Contrast
http://study.com/academy/lesson/electric-motors-generatorsconverting-between-electrical-and-chemical-energy.html
Electricity
- Electricity From Magnetism
Transformers
A transformer is a device that increases or decreases
voltage.
Electricity
- Electricity From Magnetism
Types of Transformers
Voltage can be changed depending on the number of loops
in the primary and secondary coils.