Electricity & Magnetism
Electricity & Magnetism
Properties of Magnets:
Magnet: any material that attracts iron and materials that contain iron Magnets attract iron and materials that contain iron. magnets attract or repel other magnets. In addition, one part of a magnet will always point north when allowed to swing freely.
Magnetic Pole: any magnet with 2 ends, each is called a magnetic pole. Magnetic poles that are unlike attract each other and magnetic poles that are alike repel each other. Magnetic Force: the attraction or repulsion between magnetic poles
Magnetic Field: the area of magnetic force around a magnet
Magnetic Field Lines:
invisible lines that map out the magnetic field around a magnet. Magnetic field lines spread out from one pole, curve around the magnet, and return to the other pole.
Atom: the smallest particle of an element
Element: basic substances that make up all matter.
Nucleus: center region of the atom
Protons: particle that is positive
Neutron: Particle that has no charge
Electron: particle that is negative
A spinning electron produces a magnetic field that makes the electron behave like a tiny magnet in an atom.
Magnetic Domain: grouping of atoms that have their magnetic feilds aligned In a magnetized material, all or most of the magnetic domains are arranged in the same direction. Ferromagnetic Material: A material that shows strong magnetic properties.
Making and Changing Magnets
Magnets can be made, destroyed or broken apart.
Temporary Magnet: magnet made from a material that easily loses its magnetism
Permanent Magnet: Magnet made from a material that keeps its magnetism for a long time Magnetic Earth:
Compass: a device that has magnetized needle that spins freely Earth as a Magnet:
Just like a bar magnet, Earth has a magnetic field surrounding it 2 magnetic poles Magnetic Declination: the angle (at a particular location) between magnetic north and true north Earth’s Magnetic Field:
Since Earth produces a strong magnetic field, Earth itself can make magnets out of ferromagnetic materials. The Magnetosphere Earth’s magnetic field affects the movements of electrically charged particles in space. Van Allen belts: between 1,000-25,000 km above Earth’s surface are 2 doughnut-shaped regions Solar Wind: stream of electrically charged particles flowing at high speeds from the sun Magnetosphere: Earth’s magnetic field shaped by the solar wind Aurora: glowing region in the atmosphere caused by charged particles from the sun
Charges that are the same repel each other.
Charges that are different attract each other.
Electric Force: attraction or repulsion between electric charges Electric Field: extends around a charged object
An electric field is a region around a charged object where the object’s electric force is exerted on other charged objects.
Static Electricity: the buildup of charge on an object
In static electricity, charges build up on an object, but they do not flow continuously.
Law of Conservation of Charge: charges are neither created nor destroyed There are three methods by which charges can be transferred to build up static electricity: charging by friction, by conduction, and by induction. Charging by friction: the transfer of electrons from one uncharged object to another by rubbing Charging by conduction: the transfer of electrons from a charged object to another object by direct contact Charging by induction: the movement of electrons to one part of an object that is caused by the electric field of a second object
When a negatively charged object and a positively charged object are brought together, electrons transfer until both objects have the same charge. Static Discharge: the loss of static electricity as electric charges transfer from one object to another
Flow of Electric Currents:
Electric Current: the continuous flow of electric charges through a material To produce electric current, charges must flow continuously from one place to another. Electric Circuit: a complete, unbroken path through which electric charges can flow
Conductors and Insulators:
A conductor transfers electric charge well.
An insulator does not transfer electric charge well.
Conductor: a material through which charge can flow easily
Insulator: a material through which charges cannot flow easily
Voltage: difference in electrical potential energy between 2 places in a circuit Also called potential difference
variable is V
Voltage causes a current in an electric circuit.
Voltage Source: a device that creates a potential difference in an electric circuit
Resistance: the measure of how difficult it is for charges to flow through a material Omega
The greater the resistance, the less current there is for a given voltage.
Ohm’s law says that the resistance is equal to the voltage divided by the current Ω=VA
Features of a Circuit:
First, circuits have devices that are run by electrical energy. Second, a circuit has a source of electrical energy.
Third, electrical circuits are connected by conducting wires.
Series Circuit: if all the parts of an electric circuit are connected one after the other along one path In a series circuit, there is only one path for the current to take.
Ammeter: a device used to measure current.
Parallel Circuit: the different parts of the circuit are on separate branches In parallel circuit, there are several paths for current to take. Voltmeter: a device used to measure voltage, or electrical potential energy.
You can calculate power by multiplying voltage by current.
Power = Voltage x Current
P = VI
Paying for Electrical Energy:
The total amount of energy used by an appliance is equal to the power of the appliance multiplied by the amount of time the appliance is used. Energy = Power x Time
Kilowatt-hours = Kilowatts x Hours
Short Circuit: connection that allows current to take the path of least resistance One way to protect people from electric shock and other electrical danger is to provide an alternate path for electric current Grounded: when charges are able to flow directly from the circuit into Earth in the event of a short circuit Third Prong: (round) connects any metal pieces of the appliance to the grounded wire of the building
Breaking A Circuit
In order to prevent circuits from overheating, devices called fuses and circuit breakers are added to circuits Fuse: a device that contains a thin strip of metal that will melt if there is too much current through it Fuses are no longer used because it can be difficult to replace them Circuit Breaker: a reusable safety switch that breaks the circuit when the current gets too high
Electric Current and Magnetism
An electric current produces a magnetic field
Electromagnetism: relationship between electricity and magnetism
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 Solenoid: a coil of wire with a current
Electromagnet: a solenoid with a ferromagnetic core
An electromagnet is a strong magnet that can be turned on and off.
Electrical Energy and Motion:
Energy: the ability to move an object over a distance
Electrical Energy: the energy assiciated with electric currents When a wire with a current is placed in a magnetic field, electric energy is transformed into mechanical energy.
Galvanometer: a device that measures small currents
An electric current is used to turn the pointer of a galvanometer.
Electric Motor: a device that uses an electric current to turn an axle An electric motor transforms electrical energy into mechanical energy.
Induction of Electric Current:
An electric current is induced in a conductor when the conductor moves through a magnetic field. Electromagnetic Induction: generating an electric current from the motion of a conductor through a magnetic field Direct Current: a current consisting of charges that flow in one direction only Alternating Current: the induced current in the wire would reverse direction repeatedly An alternating current consists of charges that move back and forth in a circuit.
Electric Generator: a device that transforms mechanical energy into electrical energy A generator uses motion in a magnetic field to produce an electric current.
A transformer is a device that increases or decreases voltage. Transformer: consists of 2 seperate coils of insulated wire wrapped around an iron core Step-Up Transformer: a transformer that increases voltage
Step-Down Transformer: a transformer that decreases voltage
the electrical force in an electrical current will align magnetic domains.