1. Teaching note Just in case you have never tried this before. This is split into 6 spaced learning presentations. The idea is that each one is presented and the students focus on remembering the key words that are highlighted red. After each run through a completely unrelated task (the more quirky the better) is given to allow for processing time and then a run through trying to remember the key points is completed. Blue slides separate the tasks.

2. P2 Spaced Learning All you need to do is remember the red highlighted words!

3. P2 Spaced Learning All you need to do is remember the red highlighted words!

4. P2 Topic 2 Controlling & using electrical current

5. Series Circuit – 1 bulb As electrons flow through a power source they gain energy. This energy is lost as the electrons transfer energy to the components in the circuit. The potential difference (PD/V) is the difference in energy before and after a component. Work Done (joules, J) Charge (Coulombs, C) Potential Difference (Volts, V)

6. Voltmeters must be connected in parallel to measure potential difference (Voltage), symbol PD or V, unit V or volts.

7. Ammeters must be connected in series to measure current, symbol I, unit A or amps.

8. The current flowing into a junction must equal the current leaving a junction. It must go somewhere! Current will always try to take the easiest (least resistance) route. Current (I, Amps [A]), Potential Difference/Voltage (PD/V, Volts [V]) and Resistance (R, Ohms[Ω]) are linked together by Ohm’s Law: V = I x R If one changes at least one of the others must change !!

9. You need to know the following electrical components

10. As the free electrons move through components they hit other electrons and atoms. As they do this they transfer a little bit of their energy and this causes atoms in the component to heat up/vibrate making it more difficult for electrons to pass without hitting them. This means that the charges (Electrons) lose a bit of energy and the potential difference across components increases with resistance as more work has to be done (or energy transferred) to pass through the component.

11. This graph shows a directly proportional relationship (Straight line going through the origin) between PD and current. This is for an Ohmic resistor (most resistors are Ohmic) at a constant temperature. The steeper the line the lower the resistance the less steep the line the higher the resistance. Lower Resistance Higher Resistance This gives Ohm’s law and V = IR

12. When the PD is negative or reverse biased only a small current flows (0.001mA). As the PD becomes positive or forward biased initially only a small current flows until the threshold voltage is reached. After this point small increases in potential difference produce large increases in current as the resistance reduces. Threshold Voltage Forward Biased Reverse Biased The steeper the line the lower the resistance the less steep the line the higher the resistance. A diode and LED operate in the same way

13. As the voltage is increased (positively or negatively) the current also increases. Initially this increase is directly proportional. As the bulb glows some of its energy is transferred into heat. This causes atoms in the filament to vibrate more quickly. Electrons are trying to pass through the filament and these are obstructed by the atoms vibrating. This means the electrons slow and transfer more energy. This in turn means less current gets through. This reduced ability for electrons to pass causes the curve as current reduces caused by an increase in resistance or increased loss in heat energy. The steeper the line the lower the resistance the less steep the line the higher the resistance. Directly proportional region

14. Light Dependent Resistor (LDR) Light intensity increases i.e. it gets brighter Resistance decreases LDRs can be used as light sensitive switches. Street lamps for example use them to switch lights off during the day

15. Thermistor Temperature Increases Resistance decreases Thermistors can be used as temperature sensors. Cars use them to sense if the engine needs cooling (temp range -90 o C to 200 o C)

17. Task for you ! Make a models of free electrons passing through a light bulb with the materials provided!!

18. What can you remember?

19. Series Circuit – 1 bulb As electrons flow through a power source they gain energy. This energy is lost as the electrons transfer energy to the components in the circuit. The potential difference (PD/V) is the difference in energy before and after a component. Work Done (joules, J) Charge (Coulombs, C) Potential Difference (Volts, V) 1 2 3 4 5 6

20. Voltmeters must be connected in parallel to measure potential difference (Voltage), symbol PD or V, unit V or volts. 1 2 3

21. Ammeters must be connected in series to measure current, symbol I, unit A or amps. 1 2 3

22. The current flowing into a junction must equal the current leaving a junction. It must go somewhere! Current will always try to take the easiest (least resistance) route. Current (I, Amps [A]), Potential Difference/Voltage (PD/V, Volts [V]) and Resistance (R, Ohms[Ω]) are linked together by Ohm’s Law: V = I x R If one changes at least one of the others must change !! 1 2 3 4 5

23. You need to know the following electrical components

24. As the free electrons move through components they hit other electrons and atoms. As they do this they transfer a little bit of their energy and this causes atoms in the component to heat up/vibrate making it more difficult for electrons to pass without hitting them. This means that the charges (Electrons) lose a bit of energy and the potential difference across components increases with resistance as more work has to be done (or energy transferred) to pass through the component. 1 2 3 4

25. This graph shows a directly proportional relationship (Straight line going through the origin) between PD and current. This is for an Ohmic resistor (most resistors are Ohmic) at a constant temperature. The steeper the line the lower the resistance the less steep the line the higher the resistance. Lower Resistance Higher Resistance This gives Ohm’s law and V = IR 1 2 3 4 5 6

26. When the PD is negative or reverse biased only a small current flows (0.001mA). As the PD becomes positive or forward biased initially only a small current flows until the threshold voltage is reached. After this point small increases in potential difference produce large increases in current as the resistance reduces. Threshold Voltage Forward Biased Reverse Biased The steeper the line the lower the resistance the less steep the line the higher the resistance. A diode and LED operate in the same way 1 2 3 4 5 6 7 8

27. As the voltage is increased (positively or negatively) the current also increases. Initially this increase is directly proportional. As the bulb glows some of its energy is transferred into heat. This causes atoms in the filament to vibrate more quickly. Electrons are trying to pass through the filament and these are obstructed by the atoms vibrating. This means the electrons slow and transfer more energy. This in turn means less current gets through. This reduced ability for electrons to pass causes the curve as current reduces caused by an increase in resistance or increased loss in heat energy. The steeper the line the lower the resistance the less steep the line the higher the resistance. Directly proportional region 1 2 3 4 5 6 7

28. Light Dependent Resistor (LDR) Light intensity increases i.e. it gets brighter Resistance decreases LDRs can be used as light sensitive switches. Street lamps for example use them to switch lights off during the day 1 2 3 4

29. Thermistor Temperature Increases Resistance decreases Thermistors can be used as temperature sensors. Cars use them to sense if the engine needs cooling (temp range -90 o C to 200 o C) 1 2 3 4

30. 1 2 3 4