 # Unit 10 - Electricity.

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Unit 10 - Electricity

What is electricity? Electricity – form of energy caused by moving electrons

The Atom the atom has three basic parts Proton Neutron Electron

The Atom the protons and neutrons are found in the nucleus
the electrons are found in a cloud around the nucleus

The Atom Protons have a positive (+) charge
Electrons have a negative (-) charge Neutrons are neutral

The Atom objects with the same charge repel, or move away from, each other objects with different charges attract each other most objects are electrically neutral

The Atom Electrons can move from place to place
Electrons always move from a negatively charged area to a positively charged area this movement of electrons is the basis of electricity

Insulators & Conductors
Conductors – materials that allow electric charges to flow through them easily

Insulators & Conductors
some conductors are better than others most metals are good conductors of electricity

Insulators & Conductors
Insulators – materials that prevent electric charges from flowing through them easily

Insulators & Conductors
some examples of insulators include: rubber cork wood plastic

Insulators & Conductors
electric wires use both insulators and conductors a conductor, often a copper wire, is coated with an insulator, such as rubber if the insulator wears out and the wires come in contact, a short circuit occurs, allowing the electricity to jump between the wires

Electric Current electric current – flow of electrons through a conductor the number of electrons flowing determines the amount of electric current there are two types of electric current: Direct Current Alternating Current

Electric Current direct current – current in which electrons always flow in the same direction current always flows from the negative pole to the positive pole all batteries provide direct current

Electric Current alternating current – current in which electrons change direction at a regular rate most electricity that is used in everyday life comes from alternating current

Electric Current alternating current produces less heat, when carried by wires from power plants, then direct current this results in less damage to power cables

Batteries battery – series of electrochemical cells connected together
electrochemical cell – device that changes chemical energy into electrical energy a battery is a source of direct current

Batteries when you connect the negative and positive poles of a battery to a conductor, electric current flows through the conductor

Batteries there are two types of batteries: wet cells dry cells

Batteries the simplest type of electrochemical cell is called a wet cell a wet cell has three parts: negative pole positive pole electrolyte

Batteries electrode – positive or negative pole of an electrochemical cell the negative electrode is often made of zinc the positive electrode is often made of copper

Batteries electrolyte – substance that dissolves in water to form a conducting solution sulfuric acid is often used as an electrolyte

Batteries a chemical reaction in the wet cell causes electrons to build up on the zinc electrode when the two electrodes are connected by wire, electrons flow from the zinc to the copper electrode

Batteries the most familiar type of electrochemical cell is called a dry cell a dry cell works the same way as a wet cell with a positive electrode, a negative electrode, and an electrolyte

Batteries the electrolyte is a moist paste inside the cell
the negative electrode is the outside case of the battery which is usually made of zinc the positive electrode is located inside the battery and is sometimes made of carbon

Batteries newer style dry cell batteries use nickel oxide for a positive electrode and cadmium for a negative electrode these are called nickel-cadmium, or ni-cad, batteries

Electric Circuits electric circuit – path that an electric current follows all electric circuits have three parts source of electric current load (something that uses electricity) wires (connect the source to the load) most electric circuits also have a switch

Electric Circuits there are two types of electric circuits
series circuit parallel circuit

Electric Circuits series circuit – circuit in which electric current follows only one path a series circuit is the simplest type of electric circuit

Electric Circuits parallel circuit – circuit in which electrical current can follow more than one path if several appliances are connected in a parallel circuit, current can still reach the other appliances if one of them stops working parallel circuits are used in homes, schools, and office buildings

Volts, Amps, & Ohms electromotive force – force that makes electrons move electromotive force is abbreviated EMF

Volts, Amps, & Ohms volt – unit used to measure electromotive force
voltage is measured with a voltmeter

Volts, Amps, & Ohms ampere – unit used to measure electric current
one ampere, or amp, is the amount of current passing a point each second

Volts, Amps, & Ohms the amount of electric current depends on the number of electrons flowing in a circuit current is measured with an ammeter

Volts, Amps, & Ohms as current flows through a wire, it meets resistance from the wire

Volts, Amps, & Ohms resistance – opposition to the flow of electric current Ohm – unit used to measure resistance

Volts, Amps, & Ohms resistance of a wire depends on: length thickness
material temperature

Volts, Amps, & Ohms length – the longer a wire is, the more resistance it has width – the thinner a wire is, the more resistance it has material – wires made of poor conductors have more resistance than wires made of good conductors temperature – as a wire gets hotter, its resistance increases

Volts, Amps, & Ohms every closed circuit has: current (I) voltage (V)
resistance (R)

Volts, Amps, & Ohms different power sources have different amounts of voltage the resistance varies depending on the type of wires used the current is affected by the voltage and the resistance

Ohm’s Law Ohm’s law – current in a wire is equal to the voltage divided by the resistance current = voltage / resistance I = V/R

Ohm’s Law

Electric Safety too much current in a circuit can cause an overloaded circuit electric current comes into a house from power lines to a breaker box

Electric Safety breaker boxes contain: fuses or circuit breakers

Electric Safety fuse – wire that melts and breaks a circuit if too much current is flowing by melting, the fuse stops current from flowing and prevents an overloaded circuit fuses need to be replaced when they become overloaded fuses are used in many older homes

Electric Safety circuit breaker – switch that opens a circuit if too much current is flowing a circuit breaker can be reset when it becomes overloaded most newer homes have circuit breakers