PS.9 The student will investigate and understand basic principles of electricity and magnetism. Key concepts include
1. an imbalance of charge generates static electricity
2. materials have different conductive properties
3. electric circuits transfer energy
4. magnetic fields cause the magnetic effects of certain materials
5. electric current and magnetic fields are related
6. many technologies use electricity and magnetism.

Static electricity (an imbalance of charges)

• Friction can cause electrons to be transferred from one object to another.
• The resulting imbalance in static electrical charges can build up on an object and be discharged slowly or rapidly.
• This is often called static electricity .

Electric Currents

Conductors

• A conductor is a material that transfers an electric current.


Resistance increases as wire narrows or lengthens

• An insulator is material that does not transfer an electric current.
• A semiconductor is a material that is in between a conductor and an insulator in terms of transferring electric current .
• Several factors affect how much electricity can flow through a system.
• Resistance is a property of matter that affects the flow of electricity.
  • Some substances have more resistance than others .

Electrical Circuits

• Voltage is the potential difference in charge between two points.
• Current is the uniform flow of electrons through a circuit.
• Resistance is a measure of the degree to which an object opposes the passage of an electric current.




• Basic principles applicable to circuits include
  • electrons need a complete, conducting pathway (circuit)
  • electrons must receive energy (voltage) from a source
  • electrons move around the circuit, traveling from high to low potential through a device (current)
  • electrons transfer energy to perform some useful function (work)
  • thermal energy is transferred to the surroundings.
• An electronic circuit is composed of individual electronic components, such as transistors and diodes, connected by conductive wires through which electric current can flow.
• Many common devices utilize electronic circuits.

• Electronic circuits have advantages over electric circuits, providing transfer of data and miniaturization .
• Transistors are semiconductor devices made from silicon, and other semiconductor materials.
• These are used to amplify electrical signals (in stereos or radios) or to act like a light switch, turning the flow of electricity on and off .

Magnetic Fields

• The sizes of these forces depend on the magnitudes of the charges, currents, or magnetic strengths involved and on the distances between the interacting objects.
• Forces that act at a distance can be explained by fields that extend through space and can be mapped by their effect on a test object . 

•  Electric and magnetic (electromagnetic) forces can be attractive or repulsive.
• Many technologies use principles of electromagnetism to operate.
•  Moving electricity can produce a magnetic field and cause iron and steel objects to act like magnets.
• Electromagnets are temporary magnets that lose their magnetism when the electric current is removed.
• Both a motor and a generator have magnets (or electromagnets) and a coil of wire that creates another magnetic field.

• Changing magnetic fields can produce electrical current in conductors.
• This phenomenon is called electromagnetic induction.

Technologies that use Electricity and Magnetism

• A generator is a device that converts mechanical energy into electrical energy.
• Most of the electrical energy we use comes from generators.
• Electric motors convert electrical energy into mechanical energy that is used to do work.
  • Examples of motors include those in many household appliances, such as blenders and washing machines.