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Unit 10 - Electricity. What is electricity? Electricity – form of energy caused by moving electrons.

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Presentation on theme: "Unit 10 - Electricity. What is electricity? Electricity – form of energy caused by moving electrons."— Presentation transcript:

1 Unit 10 - Electricity

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

3 The Atom the atom has three basic parts –Proton –Neutron –Electron

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

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

6 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

7 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

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

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

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

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

12 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

13 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

14 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

15 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

16 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

17 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

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

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

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

21 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

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

23 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

24 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

25 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

26 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

27 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

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

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

30 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

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

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

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

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

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

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

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

38 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

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

40 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

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

42 Ohms Law Voltage (V) Current (I) Resistance (R)

43 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

44 Electric Safety breaker boxes contain: –fuses or –circuit breakers

45 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

46 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

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