Physics Paper 3 Help !

[AStarHunter]

guyz, i don`t get potential difference ! could anyone explain it to me and qs (10)(c) in this paper --->http://www.xtremepapers.me/CIE/Cambridge IGCSE/0625 - Physics/0625_w06_qp_3.pdf
thnx in advance

 

[igcse2011]

Not very sure but...
Voltage is an informal term for electric potential difference.
The amount of energy per unit charge needed to move a charged particle from a reference point to a designated point in a static electric field; voltage

 

[unplugged]

I think you mean potential divider .

In the dark the resistance of the light dependent resistor increases causing higher voltage to be delivered to the transistor and effectively allowing current to pass through it which in turn lights up the lamp.

 

[AStarHunter]

guyz, i don`t get something else :
In this paper, http://www.xtremepapers.me/CIE/Cambridge IGCSE/0625 - Physics/0625_s07_qp_3.pdf : Q(10)(b)
I got the first mark (change value of R1) but i didn`t get the second mark which is brief explanation in terms of potential divider
What are we supposed to exactly write ? use a potential divider ?
Thnx

 

[xIshtar]

Well you need to explain how modifying R1 will affect the temperature at which the lamp switches on.. You don't write you should use a potential divider, as it is already in use.
You need to relate the change in R1 to the rest of the circuit. Ie, as V=IR, if you reduce R it will reduce the voltage in this resistor. This will mean a higher voltage and resistance in the thermistor, which will mean that it will light the bulb at a lower temperature