# GCSE physics

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1. current potential difference graphs are used to
show how the curren through a component varies with the p.d. across it
2. what does the current potential difference graph look like for a resistor (metal wire) at constant temperature
• straight line through the origin , the current is directly proportional to the voltage
• 3. how do we use a currrent potential differnce graph to find the resistance
4. what can we conclude from a current potential difference graph for a resistor (metal wire) at constant temperature
OHMS LAW - the current through a resistor (at constant temperature)is directly proportional to the p.d. across the resistor
5. A) what is the conclusion to an experiment to investigate the relation between the p.d. across a filament lamp and the current through it
B) what differences have you found when the component is allowed to get hot
• A) the resistance of a filament bulb increases as the temperature of the filament increases
•  b) as the current increases it heats the filament and the resistance increases
6. what is the graph for an experiment to investigate the relation between the p.d. across a filament lamp and the current through it 7. what is a dioide
• it is a component that allows current through itself in one directiom but not the other
• diodes convert alternating current into direct current
8. this graph shows that as the current increases , the resistance of the filament
increases because as the current increases it heats the wire and the resistance increases
9. Faced with the arrow head pointing to the right the diode has a ........ Resistance . A ....... .... and the bulb ....... Light up . We say the diode is ..... .....
• Low
• cureent flows
• does
• forward biased
10. faced with the arrow head pointing to the left the diode has a very ...... Resistance . . .... ..... Flows so the bulb ..... Light up . We say the diode is ..... ....
• High
• no current
• doesnt
• reversed biased
11. The current through a diode flows
In one direction only . The diode has a very large resistance in the reverse direction
12. What is the graph for an experiment to investigate the relation between the p.d. Across a diode and the current through it 13. For our experiment with the resistor and the filament lamp we plotted voltage on the y axis and current on the x axis . This meant that the gradient of the graph was voltage/current I.e. resistance . For the diode it is tradional to
• Plot the current on the y axis and voltage on the x axis and to show both + and - values on the graph
• you may still use reasistance = voltage/current but the gradient does not equal the resistance
14. What does LED stand for
Light emitting diode
15. An LED emits light when
A current flows through it in the forward direction
16. There is an increasing use of LED's for lighting because they
Use a much smaller current than other forms of lighting
17. What does LDR stand for
light dependant resistor
18. the resistance of A LDR decreases as
The light intensity increases
19. When you cover the LDR the light intensity
Decreases the resistance increases and the current decreases . The opposite happens when you uncover the LDR
20. what are the uses of an LDR
• Photographers light meter
• burglary alarms
• automagic hand drier
21. The resistance of a thermistor decreases as the
Temperature increases
22. When you heat a thermistor the
Resistance decreases and the current increases
23. What are the uses of a thermistor
• Electronic thermometer
• fire alarm
24. Name the comment of each phrase
a) it's resistance decreases as it gets hotter
b) it's resistance increases as it gets hotter
c) it's resistance depends on which way it is connected in a circuit
d) it's resistance increasget when you cover it
• A) thermistor
• b) lamp
• c) diode
• d) LDR
25. What ippt he graph to show how the resistance of a thermistor changes with current 26. State and explain how the current in a curcuit with a thermistor connected in a series with a cell and resistor changes when the temperature of the thermistor increases
As it gets hotter it frees more electrons to increase the current
27. A LDR connected in a series with a resistor , and ammeter and a battery . A voltmeter is connected across the resistor . Explain why the ammeter reading decreases when the LDR In daylight is covered
Because when  it is covered there is less light and  the resistance increases and the current decreases
28. For compnents connected in series
• The total resistance is the sum of the resistance of each component
• there is the same current through each component
• the p.d. Of the supply is shared between the components
29. A
 Author: ghoran ID: 172942 Card Set: GCSE physics Updated: 2012-09-24 20:43:49 Tags: Unit two part three currents electrical circuits four Folders: Description: revision Show Answers: