Electrical Power : Electrical Power Power = Work / Time
Power = Current × Voltage
What are the units for Current, Voltage, and Power?
Watt Demonstration:
Lift a 1-kg mass a distance of 1 meter, and you have done 1 Joule of Work.
Do this once each second, and your power output is 1 Watt.
Light bulbs are rated by the power used.
Chapter 12 : Chapter 12 Magnetism
Magnetism - Lab Pages : Magnetism - Lab Pages Caution Page
“No Magnets Here” Page
Sweet Tooth Magnet
Lodestone : Lodestone A Lodestone is a naturally occurring piece of magnetic iron oxide. It is often bound in a brass frame, and is oriented to place the magnetic poles at the ends.
The word magnet comes from the region called Magnesia in Asia Minor. The word lodestone comes from the use of pieces of ore from Norway and Sweden which were suspended and used as guiding or leading stone; the Saxon word Læden means "to lead".
Magnetic Compass : Magnetic Compass Some naturally occurring materials are natural magnets, a property discovered by the Chinese and used to make the first lodestone compasses.
Three Pages
Magnetic Compass Magic
Water Compass
Make a Compass (Supplement)
Use this one in your classroom.
Note
Strong magnets can be purchased from Radio Shack for about $2.
Magnetism - Section 12.1 : Magnetism - Section 12.1 The Ends of a Magnet
North-Seeking Pole or North Magnetic Pole
South-Seeking Pole or South Magnetic Pole
More simply these are called the north and south poles of a magnet.
Opposite poles of a magnet attract each other.
Like poles of a magnet repel each other.
Magnetic Fields - Section 12.2 : Magnetic Fields - Section 12.2 What would happen if you break a bar magnet between the poles?
See figure 12.2.
Must every magnet have a north and south pole?
Answer: Yes.
Magnetic “monopoles” have not been found in nature. Magnets are sometimes called “dipoles”.
This suggests that the atoms themselves are magnets.
A magnetic field is produced by the motion of electrical charge.
Electrons that are spinning and orbiting are tiny magnets. Figure 12.6.
Magnetic Fields - Section 12.3 : Magnetic Fields - Section 12.3 Large clusters of atoms line up with one another.
These clusters are called magnetic domains that can be seen with a microscope.
In magnets, all of the domains line up.
You can line up the domains in a material if you bring it close to another magnetic.
Figure 12.8.
Most common magnets contain iron, nickel, and/or cobalt.
Demo: Change the direction that the blue arrow of a magnet points.
The Earth’s Magnetic Field : The Earth’s Magnetic Field Note: The northern hemisphere of the Earth contains the south pole of the “Earth magnet”.
Draw the magnetic field lines for the Earth.
The Earth's magnetic field is similar to that of a bar magnet tilted 11 degrees from the spin axis of the earth.
The Earth's core is not magnetic. So how did the Earth get its magnetic field?
Magnetic fields surround electric currents, so we surmise that circulating electric currents in the Earth's molten metallic core are the origin of the magnetic field.
A current loop gives a field similar to that of the earth.
To what will a magnet stick? Supplemental Exercise List 10 items in each column. Examples: Copper rod, keys, coins, etc. : To what will a magnet stick? Supplemental Exercise List 10 items in each column. Examples: Copper rod, keys, coins, etc.
What makes a thing magnetic? Supplemental Exercise : What makes a thing magnetic? Supplemental Exercise
Chapter 12 : Chapter 12 Magnetism
Electric Currents and Magnetic Fields Section 12.4 : Electric Currents and Magnetic Fields Section 12.4 Moving charges in wires create magnetic fields. See Figure 12.10 and 12.11.
What is an electromagnet?
A coil of wire
It usually has an iron core.
Make and Electromagnet Supplemental Exercise : Make and Electromagnet Supplemental Exercise
Magnetic Forces on Moving Charges Section 12.5 : Magnetic Forces on Moving Charges Section 12.5 The magnetic force on a charge is always perpendicular to the magnetic field lines and the velocity of the charges.
Use the right hand rule for positive charges and the left hand rule for negative charges.
Consider an electron beam traveling through a horseshoe magnet.
Force on a Current Carrying Wire Supplemental Exercise : Force on a Current Carrying Wire Supplemental Exercise
Electromagnetic Induction Section 12.6 : Electromagnetic Induction Section 12.6 The phenomenon of inducing a voltage by changing the magnetic field in a wire is electromagnetic induction.
Examples:
Hand-held generators
Transformers
Jumping Ring and Light
Power Plants
Figure 12.26 and 12.27
Electromagnetic Induction Supplemental Exercise : Electromagnetic Induction Supplemental Exercise
Transformer Supplemental Exercise : Transformer Supplemental Exercise
How Close Can You Get Supplemental Exercise : How Close Can You Get Supplemental Exercise
Test 3 : Test 3 Chapter 11 - Electricity
Coulomb’s Law
Polarization
Current, Voltage, Resistance
Ohm’s Law
AC and DC
Series and Parallel Circuits
Batteries, Resistors, Switches, LEDs, and Bulbs
Sections 11.1 - 11.11
Test 3 : Test 3 Chapter 12 - Magnetism
Magnetic Forces and Magnetic Poles
Magnetic Fields and Magnetic Domains
Interaction between currents and magnetic fields
Electromagnets
The “right hand rule”
Electromagnetic Induction
Sections 12.1 - 12.9
MAGNETISM : MAGNETISM MAGNETISM IS PRODUCED BY MOVING CHARGES.
MAGNETIC POLES : MAGNETIC POLES THE “N” POLE OF A MAGNET MEANS THAT THIS POLE SEEKS THE NORTH POLE OF THE EARTH, IF THE MAGNET IS FREE TO ALLIGN ITSELF WITH THE EARTH’S MAGNETIC FIELD.
LAWS OF ATTRACTION : LIKE POLES REPEL
UNLIKE POLES ATTRACT LAWS OF ATTRACTION N S S N N S N S
MAGNETIC POLES : MAGNETIC POLES A MAGNET IS A DIPOLE (TWO POLE).
THERE IS NO MONOPOLE (SINGLE POLE).
CUT A MAGNET IN HALF AND YOU GET TWO DIPOLES. N S N S N S
MAGNETIC MATERIALS : MAGNETIC MATERIALS MOST MATERIALS ARE NOT MAGNETIC
NATURALLY OCURRING MAGNETIC MATERIALS ARE CALLED FERROMAGNETIC (IRON-LIKE)
FERROMAGNETIC MATERIALS ARE
IRON
COBALT
NICKLE
FERROMAGNETISM : FERROMAGNETISM ELECTRONS HAVE MAGNETIC FIELDS DUE TO THEIR SPIN AND ORBITAL MOTION.
ATOMS OF FERROMAGNETIC MATERIALS POSSESS ELECTRONS WHICH HAVE MAGNETICS FIELDS THAT DO NOT CANCEL OUT INSIDE THE ATOM.
MAGNETIC DOMAINS : MAGNETIC DOMAINS THESE ARE SMALL REGIONS IN A
FERROMAGNETIC MATERIAL WHERE
ALL THE MAGNETIC FIELDS OF THE
ATOMS ARE ALLIGNED.
MAGNETIZATION : MAGNETIZATION IF THE DOMAINS ARE ALLIGNED, THE MATERIAL IS POLARIZED AND BECOMES MAGNETIZED N S
MAKING A MAGNET : MAKING A MAGNET A PIECE OF SOFT IRON CAN BE MAGNETIZED BY RUBBING ONE END WITH ONE POLE OF A STRONG MAGNET.
EARTH’S MAGNETIC FIELD : EARTH’S MAGNETIC FIELD SINCE A NORTH SEEKING MAGNETIC POLE IS ATTRACTED TOWARDS THE EARTH’S MAGNETIC POLE LOCATED NEAR GREENLAND, THIS POLE MUST BE A MAGNETIC SOUTH POLE.
MAGNETIC FIELD : MAGNETIC FIELD IMAGINARY LINES WHICH REPRESENT THE ALLIGNMENT OF A MAGNET PLACED AT A POINT IN SPACE.
AN ARROW CAN BE DRAWN AT A POINT TO SHOW THE DIRECTION THAT THE “N” POLE POINTS N S
MAGNETIC FIELD : MAGNETIC FIELD MAGNETIC FIELD LINES POINT TOWARDS THE “S” POLE.
MAGNETIC FIELD LINES POINT AWAY FROM “N” POLES N S
MAGNETIC FIELD NEAR A WIRE : MAGNETIC FIELD NEAR A WIRE MAGNETIC FIELD ELECTRON FLOW THE FIELD NEAR A WIRE FORMS CIRCLES
AROUND THE WIRE.
FIELD DUE TO A COIL : FIELD DUE TO A COIL CURRENT IN A COIL OF WIRE PRODUCES AN ELECTROMAGNET S N ELECTRON FLOW
ELECTROMAGNET : ELECTROMAGNET A STRONG ELECTROMAGNET CAN BE PRODUCED BY USING A FERROMAGNETIC CORE.
Slide49 : ELECTROMAGNET INDUCTION A VOLTAGE WILL BE INDUCED IN A COIL WHILE A MAGNETIC FIELD MOVES THROUGH THE COIL. N S V
TRANSFORMER : TRANSFORMER TWO COILS PLACED UPON A FERROMAGNETIC MATERIAL FORMS A TRANSFORMER. V
TRANSFORMER : TRANSFORMER IF CURRENT IS PRODUCED IN ONE COIL, ITS MAGNETIC FIELD WILL MAGNTIZE THE CORE.
THE MAGNETIC FIELD OF THE CORE WILL INDUCE A VOLTAGE IN THE SECOND COIL.
THIS ONLY OCCURS WHILE THE CURRENT IS CHANGING IN THE FIRST COIL.
FORCE ON A WIRE : FORCE ON A WIRE IF THE ELECTRONS IN A WIRE CROSS MAGNETIC FIELD LINES, THE WIRE WILL EXPERIENCE A NET FORCE. N S