1. INVESTIGATION HELPS Planning your investigation

2. INVESTIGATION HELPS Introduction For a fixed resistance there is a relationship between R, V and I. Plotting a graph (V) of Voltage against current (I) gives a straight line so the two quantities current and voltage are proportional. This is called Ohm’s Law after the scientist Georg Ohm. voltage = current x resistance V = I x R

3. INVESTIGATION HELPS Ohm’s Law The current flowing through a wire is proportional to the potential difference (voltage) across it provided the temperature remains constant. Current / A Potential difference / V So if voltage doubles then the current doubles and so on. x x x x x x x x Plot the current and voltage readings for a resistor on a graph and draw a line of best fit. The graph is a straight line so the two quantities current and voltage are proportional. This is called Ohm’s Law after the scientist Georg Ohm. Current-voltage graph for a resistor

4. INVESTIGATION HELPS What are the units of voltage, current and resistance? The resistance of a conductor can be calculated using: Potential difference is measured in volts (V). Current is measured in amps (A). Resistance is measured in ohms (  ). Resistance formula This equation can also be written as: voltage = current x resistance V = I x R resistance = R = voltage current V I

5. INVESTIGATION HELPS Make it Easy for Yourself 1/ Plan out the sections 2/ Try to answer all the marking criteria

6. INVESTIGATION HELPS Make it Easy for the marker….. 1/ Number the pages 2/ Put distinct section headings

7. INVESTIGATION HELPS Talking Its obvious but …. Show you know what you are talking about!!! “I will be making a series circuit, the voltmeter will be in parallel to the wire length which is being investigated.”

8. INVESTIGATION HELPS This is chosen for you ---- Your marks are fixed at “6” … “Straight forward task of limited complexity, but requiring good precision or wide range of data” S(a) – Complexity and Demand of Task

9. INVESTIGATION HELPS FOR 8 points … “Justify the choice of equipment and technique to achieve data which is precise and reliable” S(b) – Techniques Used Make good use of your preliminary experiment … saying why you are doing it … establishing the range, working out good apparatus, finding out things that could go wrong.

10. INVESTIGATION HELPS 4 Points – This is fixed S(c) – Autonomy and independence The task is closely defined by the teacher but carried out with little further guidance

11. INVESTIGATION HELPS For 8 Points Interfering factors are reviewed and controlled or allowed for. C(a) – Control of Factors The variables that influence the resistance of a wire are ….

12. INVESTIGATION HELPS P(b) – Record to a relevant degree of accuracy... The answer is 9.4567890987654 m/s (cause that’s what my calculator says) SOME THINGS NOT TO DO….. 40 million decimal places!!!!

13. INVESTIGATION HELPS P(b) – Record to a relevant degree of accuracy... The answer is 9.4 m/s. The timer is accurate to one decimal place and the ruler is accurate to +/- 2mm. SOME THINGS TO DO ….. Work out what is appropriate accuracy..

14. INVESTIGATION HELPS “I think overall the investigation was successful but with more time I would have done better E(b) – Account for anomalies ……….. SOME THINGS NOT TO DO….. state the bloomin obvious “I think the points did not fit the line as well as I would expected because the results were slightly inaccurate in the sense of consistency”

15. INVESTIGATION HELPS E(b) – Account for anomalies ……….. “I think the points did not fit the line as well ………this may be due to a lot of things however I believe it may be something to do with the battery pack….. We went on to test the battery and …. SOME THINGS TO DO ….. Pursue/test out anomalies http://www.ncsu.edu/labwrite/res/gt/gt-stat-home.html

16. INVESTIGATION HELPS I(a) Error Bars http://www.ncsu.edu/labwrite/res/gt/gt-stat-home.htm REQUIRES STANDARD DEVIATION