IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => IGCSE/ GCSE => Sciences => Topic started by: 6394 on May 24, 2010, 06:53:16 am
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like in 1st attachmnt
if light intensity is more den de resistance across LDR is less <corrct>
dat means more current n more voltage will pass thru LDR <ryt??>
but if it is dark more resistance ,thus less current n more voltage .so LDR remains off
i dnt get ths part:--->but if we chng the position of Ldr like in 2nd attachmnt in dark more resistance so the LDR switches on how n y
ISNT the current n voltage still low????
:S
Thanks
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:p
ATTACHMENTS HRE
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attachmnt 2 here
lol =D
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wid thermistor wen its like in the 3rd attachment the heat intensity is high n resistance is low thus currnt flows arnd the circuit
n wen its opp i.e less ht intnsity high res. no currnt flows arnd the circuit so circuit <output> remains off
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but wen its attached hte othr way round <attachmnt 4> less temp hi resistance, the output is switchd on. is this bcoz the resistance thru thermistor is high so the current takes the other route????????
lol dats wat my imagination says for thrmistor duno whethr m ryt or not!!!! :S
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THERMISTOR
As the temperature increases, the resistance in the thermistor decreases. It is a definiton, as thermistor is made up of semi-conductors.
The lower part of the circuit gets more share of the resistance (note that this part must NOT be connected to a transistor), more current can then flow through it, thus switching on the lamp.
LDR
As the light intensity decreases, the resistance increases.
The part of the circuit with the LDR gets more share of the resistance (note that this part must be connected to a transistor), more current can then flow through it, thus switching on the lamp.
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THERMISTOR
As the temperature increases, the resistance in the thermistor decreases. It is a definiton, as thermistor is made up of semi-conductors.
The lower part of the circuit gets more share of the resistance (note that this part must NOT be connected to a transistor), more current can then flow through it, thus switching on the lamp.
LDR
As the light intensity decreases, the resistance increases.
The part of the circuit with the LDR gets more share of the resistance (note that this part must be connected to a transistor), more current can then flow through it, thus switching on the lamp.
but it always is connected to the transistor
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My bad, I am referring to the upper / lower part of the circuit instead, the lower part of the circuit is connected to the base of the transistor.