1. 13/06/2016 Unit 2 – Physics for your Future N Smith St. Aidan’s (EdExcel)

2. 13/06/2016 Topic 1 – Static and Current Electricity

3. 13/06/2016 The structure of the atom ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”)

4. 13/06/2016 The structure of the atom ParticleRelative MassRelative Charge Proton1+1 Neutron10 Electron0 MASS NUMBER = number of protons + number of neutrons SYMBOL PROTON NUMBER = number of protons (obviously)

5. 13/06/2016 Static Electricity Static electricity is when charge “builds up” on an object and then stays “static”. How the charge builds up depends on what materials are used and the insulator can be charged up by friction by “transferring electrons”: + - + - + + - - - + + + - - + + + - - -

6. 13/06/2016 Static Electricity + + + - - - - - - - - -

7. Short Static Experiments 13/06/2016 Try the following quick static electricity experiments: 1)Rubbing a balloon on your jumper and “sticking” it to the wall 2)Charging a plastic rod by rubbing it with a cloth and then holding it near the water from a smooth-running tap 3)Charging a plastic rod and trying to pick up small pieces of paper (or someone else’s hair!) with it 4)Rubbing a balloon on someone else’s head – you might want to ask their permission first… Can you explain what you saw in each of these experiments?

8. Static Electricity in Lightning 13/06/2016 e-e- e-e- e-e- e-e-

9. Van de Graaf generators When a charge is neutralised by the movement of electrons either from the Earth or to the Earth we call this “earthing”

10. 13/06/2016 Using Static in Paint Sprayers Connected to negative voltage Connected to positive voltage 1)Why is the paint sprayer given a negative charge? 2)Why is the car given a positive charge?

11. 13/06/2016 Dangers of Static – fuelling lines

12. 13/06/2016 Electric Current Electric current is a flow of negatively charged particles (i.e. electrons). Note that electrons go from negative to positive -+ e-e- e-e- By definition, current is “the rate of flow of charge” Notice that the electrons from this battery only went in one direction around the circuit – this is called “direct current” (d.c.).

13. 13/06/2016 Charge (Q) As we said, electricity is when electrons move around a circuit and carry energy with them. Each electron has a negative CHARGE. Charge is measured in Coulombs (C). We can work out how much charge flows in a circuit using the equation: Q TI Charge = current x time (in C) (in A) (in s)

14. 13/06/2016 Example questions Charge (C)Current (A)Time (s) 52 0.41 200.5 50250 360 1)A circuit is switched on for 30s with a current of 3A. How much charge flowed? 2)During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for? 3)A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed?

15. 13/06/2016 Example questions Charge (C)Current (A)Time (s) 1052 0.41 200.540 500.2250 180360 1)A circuit is switched on for 30s with a current of 3A. How much charge flowed? 2)During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for? 3)A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed? 90C 200s 300C

16. 13/06/2016 Topic 2 – Controlling and Using Electric Current

17. 13/06/2016 Circuit Symbols VA Battery Cell Fuse Resistor LDR Voltmeter Ammeter Variable resistor Diode Switch Bulb Thermistor

18. 13/06/2016 Basic ideas… Electric current is when electrons start to flow around a circuit. We use an _________ to measure it and it is measured in ____. Potential difference (also called _______) is how big the push on the electrons is. We use a ________ to measure it and it is measured in ______, a unit named after Volta. Resistance is anything that resists an electric current. It is measured in _____. Words: volts, amps, ohms, voltage, ammeter, voltmeter

19. 13/06/2016 More basic ideas… If a battery is added the current will ________ because there is a greater _____ on the electrons caused by a greater potential difference If a bulb is added the current will _______ because there is greater ________ in the circuit

20. 13/06/2016 Current in a series circuit If the current here is 2 amps… 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

21. 13/06/2016 Current in a parallel circuit A PARALLEL circuit is one where the current has a “choice of routes”. Notice how current is “conserved” at each junction: Here comes the current… And the rest will go down here… Half of the current will go down here (assuming the bulbs are the same)…

22. 13/06/2016 Current in a parallel circuit If the current here is 6 amps The current here will be… And the current here will be…

23. 13/06/2016 Some example questions… 3A6A 1A each 4A 2A

24. 13/06/2016 Voltage in a series circuit V VV If the voltage across the battery is 6V… …and these bulbs are all identical… …what will the voltage across each bulb be? 2V

25. 13/06/2016 Voltage in a series circuit V V If the voltage across the battery is 6V… …what will the voltage across two bulbs be? 4V

26. 13/06/2016 Voltage in a parallel circuit If the voltage across the batteries is 4V… What is the voltage here? And here? VV 4V

27. 13/06/2016 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”

28. 13/06/2016 An example question: V1V1 V2V2 6V 3A A2A2 A3A3 V3V3 A1A1 2A 1A 6V 3V

29. 13/06/2016 Another example question: V1V1 V2V2 10V 3A A2A2 A3A3 V3V3 A1A1 1.2A 1.8A 6.7V 5V

30. 13/06/2016 Energy and charge The amount of energy that flows in a circuit will depend on the amount of charge carried by the electrons and the voltage pushing the charge around: W QV Energy transferred = charge x voltage (in J) (in C) (in V) By definition then, voltage means “energy transferred per unit charge” and 1V = 1J/C

31. 13/06/2016 Example questions 1)In a radio circuit a voltage of 6V is applied and a charge of 100C flows. How much energy has been transferred? 2)In the above circuit the radio drew a current of 0.5A. How long was it on for? 3)A motor operates at 6V and draws a current of 3A. The motor is used for 5 minutes. Calculate: a) the charge flowing through it, b) the energy supplied to it 4)A lamp is attached to a 12V circuit and a charge of 1200C flows through it. If the lamp is on for 10 minutes calculate a) the current, b) the energy supplied to the bulb. 600J 200s 2A, 14,400J 900C, 5400J

32. 13/06/2016 Georg Simon Ohm 1789-1854Resistance Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me. The resistance of a component can be calculated using Ohm’s Law: Resistance = Voltage (in V) (in  )Current (in A) V RI

33. 13/06/2016 An example question: V A 1)What is the resistance across this bulb? 2)Assuming all the bulbs are the same what is the total resistance in this circuit? Voltmeter reads 10V Ammeter reads 2A

34. 13/06/2016 More examples… 12V 3A 6V 4V 2A 1A 2V What is the resistance of these bulbs?

35. 13/06/2016 Resistance Resistance is anything that opposes an electric current. Resistance (Ohms,  ) = Potential Difference (volts, V) Current (amps, A) What is the resistance of the following: 1)A bulb with a voltage of 3V and a current of 1A. 2)A resistor with a voltage of 12V and a current of 3A 3)A diode with a voltage of 240V and a current of 40A 4)A thermistor with a current of 0.5A and a voltage of 10V 20  33 44 66

36. 13/06/2016 Varying Resistance Recall our earlier idea that if you increase the number of bulbs in a circuit you increase the resistance and therefore decrease the current: The same effect is seen when using a variable resistor: Increase the resistance:

37. 13/06/2016 Resistors, bulbs and diodes

38. 13/06/2016 Current-Voltage Graphs Voltage on powerpack/V Current/AVoltage/V 12 10 … 0 … -10 -12

39. 13/06/2016 Current-voltage graphs I V I V I V 1. Resistor 3. Diode 2. Bulb Current increases in proportion to _______, provided the temperature doesn’t change As voltage increases the bulb gets ______ and _______ increases due to increased vibrations in the ions in the filament A diode only lets current go in one _______ – it has very _____ resistance in the other direction Words – resistance, high, voltage, hotter, direction

40. 13/06/2016 LDRs and Thermistors

41. 13/06/2016 Two simple components: 2) Thermistor – resistance DECREASES when temperature INCREASES 1) Light dependant resistor – resistance DECREASES when light intensity INCREASES Resistance Amount of light Resistance Temperature

42. 13/06/2016 Understanding Resistance When a voltage is applied it basically causes electrons to move towards the positive end of the battery: Notice that the ions were vibrating and getting in the way of the electrons – this is resistance. This effect causes the metal to heat up. IonsElectrons NegativePositive

43. Using this heating effect 13/06/2016 This heating effect can have its advantages and its disadvantages. For example, consider an old-fashioned light bulb: This heating effect causes the filament to emit light… …but it also causes a lot of energy to be wasted to the environment

44. 13/06/2016 Electrical Power revision The amount of power being transferred in an electrical device is given by: P IV Power = voltage x current in W in V in A 1)How much power is transferred by a 230V fire that runs on a current of 10A? 2)An electric motor has a power rating of 24W. If it runs on a 12V battery what current does it draw? 3)An average light bulb in a home has a power rating of 60W and works on 230V. What current does it draw? Power is defined as “the rate of transferring energy” and is measured in units called “Watts” (W).

45. 13/06/2016 Energy and Power The POWER RATING of an appliance is simply how much energy it uses every second. In other words, 1 Watt = 1 Joule per second Energy transferred (J) = power (W) x time (s) OR Energy (J) = current (A) x voltage (V) x time (s)

46. 13/06/2016 Some example questions 1)A battery gives out a current of 0.2A and has a voltage of 1.5V. If it is used for 30 seconds how much energy has it transferred? 2)An electric fire runs at a voltage of 230V and a current of 8A. If it is left on for 2 hours how much electrical energy has it transferred? 3)A toaster transfers 20,000J of electrical energy. If it runs at a voltage of 230V and a current of 2A how long was it on for? 4)A light bulb is left on overnight for 8 hours. If it transfers 1,000,000J of energy and runs on a voltage of 230V what current did it draw? 9J 13.2MJ 43.5s 0.15A

47. 13/06/2016 Topic 3 – Motion and Forces

48. 13/06/2016 Some subtle differences… “Distance” is how far you have gone, “displacement” is how far you are from a point and can be positive or negative: Start 1 metre -1 metre Distance = Displacement = Distance = Displacement = Distance = Displacement = Distance = Displacement =

49. 13/06/2016 Some subtle differences… “Speed” means “how fast you are going”, “velocity” means “how far you are going in a certain direction”. If the following journeys take 1 second then work out: Start 1 metre -1 metre Speed = Velocity = Speed = Velocity = Speed = Velocity = Speed = Velocity =