Electricity Chapter 20

What is an electric charge/current? Charged parts of an atom either positive (+) or negative (-) What is an atom? Basic particles from which all elements are made. Made up of protons, neutrons, and electrons. What is an element? A pure substance that cannot be broken down into any other parts. Ex. Hydrogen (H).

Protons (P+) Electrons (e-) Neutrons (No) It takes an equal number of protons and electrons to complete a stable atom with neutrons filling in the cracks for more stability.

How do electric charges interact? Two positive charges repel Two negative charges repel Positive and negative charges attract

Where do you see charges? North/South pole northern lights Magnets Batteries Electrical outlets Brain and spinal cord Atoms Static electricity

Electric Charges These positive and negative charges are seen and act over a particular force and field.

What is a Force? A push or pull exerted over a distance In electricity you have an electric force, which is an attraction or repulsion between electric charges. This force is seen over a distance. This distance that the electric force acts is called the electric field.

Electric Fields

Combined + and – electric fields

Multiple charge Electric Fields

Static Electricity The buildup of charge on an object. “Static” – means not moving In static electricity, charges build up on an object, but they do not flow continuously.

Transferring Charge – if one object loses an electron the other object gains the electron. Charging by Frictions – the transfer of electrons by rubbing. Ex. rubbing a balloon on your clothes or socks on the carpet Charging by Conduction – charging by direct contact rubbing your feet on the floor. Charging by Induction – the movement of electrons to one part of an object that is caused by the electric field of a second object. Touching a doorknob.

Static Discharge The loss of static electricity as electric charges transfer from one object to another. Ex. Lightning, forms when electrons travel through the air between clouds and Earth.

Electric Current The continuous flow of electric charges through a material Measured in amps The number of amps describes the amount of charge flowing past a given point each second.

Current in a Circuit To produce electric current, charges must flow continuously from one place to another using a circuit.

Conductors and Insulators Conductors – materials in which charge can easily flow. Iron, metals, silver, copper, etc. Insulators – a material through which charges cannot flow. Rubber, plastic, glass, wood, etc.

Voltage Voltage causes current in an electric circuit. Voltage is the difference in electrical potential energy between two places in a circuit.

Resistance The measure of how difficult it is for charges to flow through a material. The greater the resistance, the less current there is for a given voltage, measured in Ohm’s. A resistor in the circuit is the item being turned on, ex. light bulb, flash light, etc.

Ohm’s Law Resistance (ohms) = Voltage (volts) Current (amps) Units of measure are: Ohm’s = volts amps Voltage = Current x Resistance

Circuits Circuits allow a connection for electricity to flow. There are two types of circuit connections.

Series Circuit Only one path for current to take

Parallel Circuit There are several paths for current to tatke

Power and Energy Measured in watts, the rate at which energy is transformed from one form to another. Power (P) = Voltage (V) x Current (I) Units of measure; watts = volts x amps Energy = Power x Time Units of measure; kilowatt-hours(kWh) = kilowatts x hours