Principles of Energy and Matter
What is energy?
Energy - The capacity for doing work.
Kinetic Energy - Energy an object has due to its motion. Potential Energy - Energy an object has because of its position or state. Mechanical Energy - Energy that an object has because of its motion and its position. Chemical Energy - Energy that is stored in the bonds between atoms and molecules. |
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Energy Forms and Transformation
Use the following PowerPoint to take notes and fill out your homework sheet. Also, click here to see a video for additional information on energy and matter.
Thermal Energy
Conduction - The transfer of heat through direct contact (particles collide). It works best in solids and liquids.
Convection -The flow of currents in a liquid or gas. Warm less dense material rises and cold more dense materials sink. It moves in a circular motion. Radiation - The heat transfer through space by electromagnetic waves. Visible light, infrared and ultraviolet light are examples of radiation. |
- Heat is transferred only when two objects are at different temperatures
- Thermal energy always moves from warmer to cooler objects
- The warmer object loses thermal energy and becomes cooler as the cooler object gains thermal energy and becomes warmer.
- Energy will continue to move from a warmer object to a cooler object until both have the same temperature.
Conductors and Insulators
- Substances that transfer thermal energy very well are called Conductors.
- Substances that do not transfer thermal energy very well are called Insulators
Electric Charges
Force - Is a push or a pull.
Charge - Is a physical property Protons - Positively charged particles. Electrons - Negatively charged particles. Neutrons - No charge. |
All matter is made up of very small particles called atoms.
Atoms are made of even smaller particles called protons, neutrons and electrons. Charged objects exert a force on other charged objects. |
Charges Exert Forces
Objects that have the same charge repel each other. Each object exerts a force on the other object. These forces push the objects apart. Objects that have opposite charges are attracted to each other. Each object exerts a force on the other object. These forces pull the objects together. Because protons and electrons have opposite charges, they are attracted to each other. Without this attraction, electrons would fly away from the nucleus of an atom. |
Atoms have equal numbers of protons and electrons. Because an atom’s positive and negative charges cancel each other out, atoms do not have a charge.
An object becomes positively charged when it loses electrons.
An object becomes negatively charged when it gains electrons.
An object becomes positively charged when it loses electrons.
An object becomes negatively charged when it gains electrons.
The force between charged objects is an electric force. The greater the charges are, the greater the electric force is between objects. The closer together the charges are, the greater the electric force is between objects.
Electricity
Electrical Insulators |
Electrical Conductors |
An electrical insulator is a material in which charges cannot move easily (their electrons cannot flow freely).
Plastic, rubber, glass, wood, and air are good insulators. |
An electrical conductor is a material in which charges can move easily.
Most metals are good conductors because some of their electrons are free to move. Copper, aluminum, and mercury are good conductors. |
Mr. Magnet Homework Instruction
Magnets
A magnet is any material that attracts iron or materials containing iron.
•All magnets have two poles
•Magnets exert forces on each other •Magnets are surrounded by a magnetic field Magnetic poles are always in pairs (one north, one south).
If a magnet is broke in half, each half gains a new pole. The force can either push the magnets apart or pull them together• The magnetic force between magnets depends on how the poles of the magnets line up. Like poles repel, and opposite poles attract Opposites Attract - Field lines that curve toward each other show attraction. Likes Repel - Field lines that curve away from each other show repulsion. |
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Cause of Magnetism
Whether a material is magnetic depends on the material’s atoms.
•As electrons in atoms move around, a magnetic field is generated. The atom will then have a north and south pole. •The atoms group together in tiny areas called domains. Each domain is like a tiny magnet. •In most materials, such as copper and aluminum, the magnetic fields cancel each other out because the domains are randomly oriented (as shown below). •In materials such as iron, nickel, and cobalt, the north and south poles of the atoms in a domain line up and make a strong magnetic field (as shown in the diagram below). •The arrangement of domains in an object determines whether the object is magnetic. |
Losing Alignment•The domains of a magnet may not always stay lined up
•When domains move, the magnet is demagnetized, or loses it magnetic properties. •Dropping a magnet or hitting it too hard •Putting the magnet in a strong magnetic field that is opposite to its own •Increasing the temperature of a magnet (in higher temperatures, atoms vibrate faster so they may no longer line up). |
Making Magnets•You can make a magnet from something made of iron, cobalt, or nickel. You just need to line up the domains.
•You can magnetize an iron nail by dragging a magnet down it many times (in one direction) •The domains in the nail line up with the magnetic field of the magnet. So, the domains in the nail become aligned. •As more domains line up, the magnetic field grows stronger. |
Currents and Magnets
A single loop of wire carrying a current does not have a very strong magnetic field.
However, if you form many loops into a coil, the magnetic fields will combine creating a much stronger field.
In fact, the magnetic field around a coil of wire produces a magnetic field similar to that of a bar magnet.
The strength of the magnetic field of a coiled wire increases as more loops are used and as the current in the wire is increased.
Since an electric current can produce a magnetic field, electricity can be used to make a magnet.
An Electromagnet is a current carrying wire wrapped around an iron core.
However, if you form many loops into a coil, the magnetic fields will combine creating a much stronger field.
In fact, the magnetic field around a coil of wire produces a magnetic field similar to that of a bar magnet.
The strength of the magnetic field of a coiled wire increases as more loops are used and as the current in the wire is increased.
Since an electric current can produce a magnetic field, electricity can be used to make a magnet.
An Electromagnet is a current carrying wire wrapped around an iron core.