Resistors Lamps and Diodes

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  • Created by: KatyN
  • Created on: 09-12-14 21:12

Resistors

A resistor is an electrical componant that restricts the flow of electric current. 

the current flowing through a resistor at a constant temperature is directly proportional to the potential difference across it-----Ohms Law

A graph with current on the y axis and voltage on the x axis. A diagonal line goes through the graph at 45 degrees. (http://a.files.bbci.co.uk/bam/live/content/z9n97ty/small)

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Filament Lamps

 Heats up when electric current passes through

lamp resistance increases as the temperature increases. Current flowing is not directly proportional to the voltage accross it. 

A graph with current on the y axis and potential difference on the x axis for a filament lamp. A curved line goes through the graph at 45 degrees. (http://a.files.bbci.co.uk/bam/live/content/z8f8mp3/small)A circle with a cross inside, centred on a horizontal line. (http://a.files.bbci.co.uk/bam/live/content/zksk2hv/small)

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Diodes

A diode has a very high resistance in one direstion, meaning current only ever flows in the other direction. Good for warning lights etc

 A graph with current on the y axis and potential difference on the x axis for a diode. A line travels along the x axis until it passes the y axis where it curves sharply upward. (http://a.files.bbci.co.uk/bam/live/content/zwvw6sg/small)A circle with a triangle inside, centred on a horizontal line. (http://a.files.bbci.co.uk/bam/live/content/zdydxnb/small)

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LEDs Lamps

Light emitting Diodes (LEDS) produce light when a current flows through them in a forward direction

Often used as indicator lights. Use much smaller current, increased use 

A circle with a triangle inside, centred on a horizontal line. Outside the circle to the top right are two arrows pointing out. (http://a.files.bbci.co.uk/bam/live/content/zj3jtfr/small)

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Thermistors and LDRs

Thermistors are used as temperature sensors, eg fire alarms. The resistance decreases as the temperature increases

 A wide rectangle centred on a horizontal line, with a line cutting across at 45 degrees from bottom to top. This line levels off to the bottom left. (http://a.files.bbci.co.uk/bam/live/content/zqbqhyc/small)

LDRs are used to detect light levels, eg auto security lights. The resistance decreaes as the light intensity increases.

A wide rectangle centred on a horizontal line, enclosed in a circle. Two arrows at the top left are pointing down and right at the circle. (http://a.files.bbci.co.uk/bam/live/content/z7g7pv4/small)

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