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Physics, Chemistry and Biology: Post your doubts here!

Mustafa omar

Mustafa omar

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ZainH said:
For 6)b)i) you can clearly tell from the diagram it's 90 degrees.
For b)ii) They mention in the question "at an angle of 43 degrees the ray is partially reflected", meaning the critical angle has to be something a little more then that or it could be 43.
For b)iii) Now that you have the angle of incidence and refraction just use the formula!
Click to expand...
Thx a lot but what's the formula they used in b iii ?
 
Moi

Moi

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Small question ! In LDR , when there is light and resistance falls, what happens to the voltage ? Increase or decrease? (is it proportional or not?)
Same question for the Thermistor ! Thx
 
ZainH

ZainH

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Moi said:
Small question ! In LDR , when there is light and resistance falls, what happens to the voltage ? Increase or decrease? (is it proportional or not?)
Same question for the Thermistor ! Thx
Click to expand...

Decreases, just remember the equation! V= IxR.
 
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ZainH

ZainH

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Moi said:
Actually, you said the thermistor correct , but the second point you talked about is the relay switch, not a transisitor !!
A transisitor, is a semiconductor device that works as a switch and has three parts, base, collecter and emitter.
Usually it's used in LDR (Light Dependent Resistor) <-- When lisht intensity increase, resistance falls and vise versa :)
Click to expand...

The 2nd point was about a transistor, here is the definition STRAIGHT from my book.

"An electronic device in which a tiny current controls a much larger current and in which the larger current can be switched on or off by switching the smaller current on or off."

Your right about the three terminals, but my point was about the transistor not relay..
A relay is just an electrically operated switch.
 
ZainH

ZainH

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Mustafa omar said:
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s07_qp_3.pdf
Question 8) a and c
Can u send me the answer of question a in a pic , so I can understand it more
Click to expand...

Heres the answer for part 8)a)
The ameter is connected above the battery to measure the current in the whole circuit, the variable resistor is connected before E so only it's brightness can be varied and you have to connect lamps C and D in parallel and then add a switch so they can be switched on and off seperatley.
This took a bit of time to make , hope it helped x)

EDIT: The ammeter's placing is wrong, check the person who posted below me to know where it's placed.
Untitled-6.png
 
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Stormcry72

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ZainH said:
Heres the answer for part 8)a)
The ameter is connected above the battery to measure the current in the whole circuit, the variable resistor is connected before E so only it's brightness can be varied and you have to connect lamps C and D in parallel and then add a switch so they can be switched on and off seperatley.
This took a bit of time to make , hope it helped x)
Click to expand...
the ammeter should never be in parallel with the circuit
connect the ammeter to the left or right of the power supply to get the current in the circuit :)
 
ZainH

ZainH

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Stormcry72 said:
the ammeter should never be in parallel with the circuit
connect the ammeter to the left or right of the power supply to get the current in the circuit :)
Click to expand...

Was unsure about that myself. T
Thanks for clearing it up x)!
 
ThatReallyReallyWeirdDude

ThatReallyReallyWeirdDude

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ZainH said:
Heres the answer for part 8)a)
The ameter is connected above the battery to measure the current in the whole circuit, the variable resistor is connected before E so only it's brightness can be varied and you have to connect lamps C and D in parallel and then add a switch so they can be switched on and off seperatley.
This took a bit of time to make , hope it helped x)

EDIT: The ammeter's placing is wrong, check the person who posted below me to know where it's placed.
Untitled-6.png
Click to expand...
lol I made a diagram for that question for someone else.
Sec I'll link it.
http://www.xtremepapers.com/community/threads/please-help-physics-paper-3.16346/#post-279422
 
Moi

Moi

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ZainH said:
The 2nd point was about a transistor, here is the definition STRAIGHT from my book.

"An electronic device in which a tiny current controls a much larger current and in which the larger current can be switched on or off by switching the smaller current on or off."

Your right about the three terminals, but my point was about the transistor not relay..
A relay is just an electrically operated switch.
Click to expand...

My book seems so different ! I think you're right, but for the relay, you meant electromagmagnetic operated switch ... right??
 
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