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Electricity

Electricity. Part 1. Background. Remember that atoms have protons, neutrons and electrons. Electrons are negatively charged particles that can sometimes when the situation is just right, escape from one atom and move to another! Movement of electrons is the basis of electricity.

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Electricity

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  1. Electricity Part 1

  2. Background • Remember that atoms have protons, neutrons and electrons. • Electrons are negatively charged particles that can sometimes when the situation is just right, escape from one atom and move to another! • Movement of electrons is the basis of electricity

  3. Static Electricity • An electric shock that is caused by the buildup of electrons is called static electricity • Small amounts of static can cause a slight shock like when you rub your feet along the carpet and touch someone • Large amounts of static can occur as in the case when clouds discharge static electricity in the form of lightning

  4. Static Activities

  5. About Electricity • The movement of electrons from one place to another is called electric current • Electric current is measured in amperes • When electrons travel in an electric current they follow a path called a current

  6. Closed Circuits VS Open Circuits • Electrons can only follow a complete, unbroken path called a closed circuit • Sometimes we DON’T WANT a closed circuit like when we want to turn the lights out. To do this, we can use an incomplete or Open Circuit Closed Circuit Open Circuit

  7. Confused??? • To make an open circuit into a circuit that we can use when we want, we put in switches. • When the switch is closed the circuit is now closed so that electrons can flow in an unbroken path • When the switch is open the circuit is now open so that now the current cannot flow through Switch Switch

  8. Conductors and Insulators • A conductor is any material that electricity passes through easily (metals are great conductors!) • An insulator is any material that electricity does NOT pass through easily (rubber, plastic) • Electric wires normally have a center made of conducting material but are coated with insulating material INSULATOR CONDUCTOR

  9. Resistance • In electricity, resistance is the measure of how easy or hard it is for electric current to move through a material. • Resistance is measured in Ohms • Insulators have high resistance • Conductors have low resistance

  10. Resistance Resistance of wire depends on 3 things: • The material the wire is made of (Copper is less resistant than tungsten) • The length of the wire (longer=more resistance) • The thickness of the wire (thinner=more resistance) Resistance is GOOD sometimes!...It causes electrical energy to turn into heat and light energy…without resistance many appliances in our home would not work!

  11. What have you learned??? Answer the following questions in you notes and turn in (you do NOT need to write the questions) • What is the difference between an insulator and a conductor? • Why would it be dangerous to use a cord that had it’s insulator destroyed? • What are three things that affect the resistance of a wire?

  12. Book Work! In your Physical Science book: Read lesson one and two then answer the questions on your worksheet

  13. Electricity Part 2

  14. Sources of Electrical Current • Something has to “push” electrical current in order for it to move through a circuit. • Electromotive force is the push that keeps the current flowing. This is measured in volts • When voltage is high, electrons have more energy to do work Check out your light bulbs and appliances at home….how many volts do these things use?

  15. Dry Cell Batteries • Batteries are a source of voltage and change chemical energy into electrical energy Dry cell battery—the materials in this battery are dry or paste-like Look at the batteries in our class flashlights. What kind are they? How many volts of energy do they supply?

  16. Dry Cell Batteries Parts of a dry cell battery • Positive terminal + • Zinc can • Paper liner • Cardboard casing • Carbon rod • Manganese dioxide paste • Negative terminal -

  17. Wet Cell Batteries • This is a source of electricity with a liquid center • Most wet cell batteries have a hard rubber case filled with a solution of sulfuric acid

  18. Construct a Battery Activity

  19. Direct and Alternating Current • When current flows in one direction it is called direct current or DC • Current in a wet or dry cell battery flow in one direction. • Current that changes direction regularly is called alternating current or AC. • AC is normally the type of electricity in most homes

  20. Ohm’s Law • Volts, Current (amps), and Resistance (ohms) in an electrical circuit are all related to one another • Ohm’s Law helps us put this relationship into a formula Volts (V) = Current (I)x Resistance (ohms) Or, more simply V = I x R Other options: R = V/Ior I = V/R

  21. Let’s try out the Ohm’s Law Formula (Yippeeeee!) • An electric circuit has a 1.5 volt dry-cell battery and a light bulb with 0.3 ohms of resistance. What is the circuit’s current? • Current = voltage/resistance • Current = 1.5 volts/.3 ohms • Current = 5 amps

  22. Ohms Practice Worksheet

  23. Series Circuit • A series circuit is a circuit in which all current flows through different electrical devices (such as light bulbs) in a single path Draw a series circuit!

  24. Series Circuit Disadvantages • If one light is unscrewed or burns out all of the other lights will go out • The more devices in the series, the less electricity goes to each device (2 lights in a circuit would be give off brighter light than 5 lights in a circuit)

  25. Batteries in Series Circuits • Batteries can be connected to series circuits and will increase the voltage in the circuit • To find the total voltage in a circuit that included multiple batteries, add the voltages of each battery together.

  26. Fuses and Circuit Breakers in Series Circuits • Homes that contain series circuits have fuses and circuit breakers to protect them • Fuses and Circuit Breakers in a series circuit help prevent fires • YOUTUBE VIDEO??

  27. Fuses and Circuit Breakers in Series Circuits • If a wire gets too hot thefusewill melt and break the circuit. Then the fuse must be replaced • Circuit breakers are switch-like devices that can be reset after the circuit has been repaired • Do you know where your house’s circuit breakers or fusebox is?

  28. Parallel Circuits • Parallel circuits are circuits in which there is more than one path for current • This can take more energy to run but if one device burns out, the others will keep working • When more electrical devices are added to the same circuit then more current runs through it. As current increases wires can heat up and cause fires. Fuses and circuit breakers can help prevent this problem Draw a parallel circuit!

  29. Batteries in Parallel Circuits • Batteries can be connected in parallel lines which allows them to provide energy for a longer amount of time • A parallel connection does NOT increase the amount of voltage in the circuit

  30. Measuring Electricity • A watt is the unit used to measure electric power (check out a light bulb…the watt amount is listed on top of the bulb) • Electric power is the amount of electrical energy used in a given amount of time • A Kilowatt-hour is a unit used to measure how much electric energy is used (this is how many 1000s of watts used in an hour)

  31. Construct a Circuit Activity

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