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Static electricity and Electricity

Static electricity and Electricity. Static electricity. Lesson 1. Lesson 1+ 2 aims. Static electricity Examples and uses of static electricity Electricity Circuits Voltage and current. Static electricity. Lesson 1. Static electricity.

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Static electricity and Electricity

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  1. Static electricity and Electricity

  2. Static electricity Lesson 1

  3. Lesson 1+ 2 aims • Static electricity • Examples and uses of static electricity • Electricity • Circuits • Voltage and current

  4. Static electricity Lesson 1

  5. Static electricity • When two different insulating materials are rubbed together they become electrically charged. • Negative charges (electrons) rub off one material onto the other. The material which gains negative charges becomes negatively charged. The material which loses negative charges becomes positively charged.

  6. Static Electricity Static Electricity

  7. Only electrons move • Both positive and negative charges are produced by the movement of electrons • Positive charges do not move • A positive static charge is caused by electrons moving away

  8. Static Electricity Static Electricity

  9. Practical 1 • Blow a balloon up, tie end up. • Rub balloon on jumper or top • Stick to wall

  10. Practical 2 • Rub plastic strips with various cloths • See which one produces static electricity • Try balloon and plastic strips near water

  11. Repel or attract • Electrically charged objects can attract small objects • Two positively charged objects will repel • Two negatively charged objects will repel • A positively charged object and a negatively charged object will attract

  12. Like charges repel Like charges repel

  13. Like charges repel Like charges repel

  14. Opposite charges attract Opposite charges attract

  15. Static Electricity Static Electricity

  16. Practical 3 • Van de Graaff

  17. Use and examples • Static electricity can be used in photocopiers, smoke precipitator, and spray painting • A charged object can be discharged by connecting it to earth with a conductor • Static electricity can be dangerous (e.g. lightning). If the voltage becomes too great the negative charges can jump a gap causing a spark. This spark could ignite a flammable liquid nearby.

  18. Electrostatic Precipitator Electrostatic precipitator

  19. Static Electricity Static electricity

  20. Static Electricity Static electricity

  21. Quiz Quiz

  22. Lesson 2 • Electricity • Circuits • Current • Voltage • Resistance

  23. Circuit Symbols Circuit symbols

  24. Switches - series circuit Switches – series circuit

  25. Switches - parallel circuit Switches - parallel circuit

  26. Conduction in metals • Metals are good conductors of electricity because they have delocalised electrons which can carry the current.

  27. Conduction in Metals Conduction in metals

  28. Conduction in liquids • Ionic compounds conduct electricity when molten or dissolved in water. The current is carried by charged particles called ions. • The positive ions (cations) attract to the negative electrode (cathode) • The negative ions (anions) attract to the positive electrode (anode) • At the electrodes the ions can lose their charge and form new substances. • This process is called electrolysis Conduction in liquids

  29. Conduction in liquids Conduction in liquids

  30. Electric current • Electric Current is the flow of charge • Current can be measured using an ammeter (connected in series) • Current is measured in Amps (A) • Increasing the Voltage will increase the current • Increasing the Resistance will decrease the current

  31. Current in a Series Circuit Current in a Series Circuit

  32. Current in a series circuit If the current here is 2 amps… The current here will be… The current here will be… And the current here will be… In other words, the current in a series circuit is THE SAME at any point

  33. Current in a parallel circuit Here comes the current… Half of the current will go down here (assuming the bulbs are the same)… And the rest will go down here… A PARALLEL circuit is one where the current has a “choice of routes”

  34. Current in circuits • In a series circuit the current is the same everywhere • In a parallel circuit the current divides on entering a junction and rejoins on returning to the battery

  35. Current in a Series Circuit Current in a Series Circuit

  36. Voltage or P.D • Potential Difference is connected to the amount of energy that is gained or lost across part of a circuit • Potential Difference is measured using a Voltmeter (connected in parallel) • Potential Difference is measured in Volts (V) • Potential Difference gained across a cell or battery is called Voltage

  37. Voltage in a series circuit V If the voltage across the battery is 6V… …and these bulbs are all identical… V V …what will the voltage across each bulb be? 2V

  38. Voltage in a series circuit V If the voltage across the battery is 6V… …what will the voltage across two bulbs be? V 4V

  39. Voltage in a parallel circuit If the voltage across the batteries is 4V… What is the voltage here? V V And here? 4V 4V

  40. P.D in circuits • In a series circuit the potential difference is shared between the components • In a parallel circuit the potential difference is the same across each component and equals the voltage across the battery

  41. Summary In a SERIES circuit: Current is THE SAME at any point Voltage SPLITS UP over each component In a PARALLEL circuit: Current SPLITS UP down each “strand” Voltage is THE SAME across each”strand”

  42. An example question: 6V A3 3A A1 V1 A2 V2 V3

  43. Answer voltage current A1-1.5A A2-1.5A A3-3A • V1-3v • V2-3v • V3-3v

  44. Advantages of parallel circuits… • There are two main reasons why parallel circuits are used more commonly than series circuits: • Extra appliances (like bulbs) can be added without affecting the output of the others • If one appliance breaks it won’t affect the others either

  45. Resistance Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me. Georg Simon Ohm 1789-1854 V Resistance = Voltage (in V) (in ) Current (in A) I R The resistance of a component can be calculated using Ohm’s Law:

  46. Resistance in circuits • Series – total resistance is equal to sum of all individual resistances (R=R1 +R2) • Parallel-1/R = 1/R1 +1/R2 etc

  47. Calculate • Q1. 1V, 1A calculate resistance • Q2. Resistance =5 ohms, I = 2.5A V=? • Q3.V=1.5V, Resistance=10ohms, I=?

  48. answers • 1ohm • 12.5V • 0.15A

  49. Resistance Resistance

  50. Lesson 3 • I-V graphs • Conductors

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