1. Additional Physics – Forces L/O :- To know how LDR’s are affected by light intensity LDR’s Exam Date -

2. L/O :- To know how LDR’s are affected by light intensity LDR’s Quick quiz: 1.What is the equation that relates current, charge and time. 2.What is the equation that relates Current, voltage and resistance? 3.Why doesn’t a filament bulb obey Ohms Law? 4.What is the job of a diode? 5.Sketch a current voltage graph for a diode.

3. In Groups An LDR is a light dependant resistor. You shine a light at it and it either increases or decreases in resistance. This is a good way of making electricity in a circuit flow depending on light levels. Write down as many uses of a light dependant electronic device as you can think of. The group with the most answers becomes Top Of The Class

4. Quick experiment. You need to set up the circuit with an LDR and shine the lamp at it at different distances. Draw a ‘SKETCH GRAPH’ of your results. Write out neatly in your books whether resistance INCREASES or DECREASES with more light.

5. TASK 1.Set up a circuit with a battery, ammeter, LDR and a voltmeter across the LDR 2.Shine the lamp over the LDR and record the current and voltage 3.Work out the resistance 4.Move the light 10cm away from the LDR and repeat Distance of lamp from LDR (m) Light intensity 1/D 2 Voltage (V)Current (A)Resistance (Ω) 0.1100 0.225 0.311.1 0.46.25 0.54

6. http://www.youtube.com/watch?feature=endscr een&NR=1&v=2n_vzqQXkkk

7. Graph your results, what do they tell you about light intensity and the resistance of an LDR How could you check the reproducibility of your results

8. Light intensity vs resistance LDR As the light level increases The resistance decreases

9. THERMISTORS A thermistor is a temperature dependent resistor. How do you think thermistors are used in ovens and fridges?

10. Next lesson: Mid topic assessment: It is a ‘how science works’ test. It doesn’t have very many ‘recall’ questions; except; The effects of adding LDRs and thermistors to a circuit. (when is the resistance high and when is it low?) The uses of LDR’s and thermistors. Things that always seem to come up: Types of error How to describe a graph for 3 marks The ‘how science works words’ on the yellow sheet at the back of your books.