Physics, Chemistry and Biology: Post your doubts here!

[ThatReallyReallyWeirdDude]

I have a question too.
The brightness of lamps and such...does it depend on current or voltage?
I think it's current, because for example if you have a variable resistor and you up the resistance, the brightness decreases because the current decreases with voltage.
Plus, current is the flow of charges and that's what supplies the energy for the lamp and other appliances.

 

[ZainH]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_31.pdf

2 (b) and (c)
need help

For 2)b)
Power = energy/time

You have the power and time so, 528*5= energy
Energy is then equal to 2640.

Now that you have energy, and there asking how many rungs he can climb in 5s , so now you have to find out the total height of the rungs. For that you need to use the formula for potential energy.
You can use the formula for potential energy since you already have the energy.

P.E= m*g*h
2640=80*10*h
2640/800 = h
h= 330

Now you have the TOTAL height, divide it by the distance that the rungs are separated by which is 30cm.
So 330/30 = 11.

He can climb 11 rungs.

 

[tribianni]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w09_qp_31.pdf Q9ci the tmprture of metal...HOW ?? asap

 

[ZainH]

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

Lol we're awesome, but your diagram > My diagram :S

 

[Mustafa omar]

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.

Man thx a lot , and it really helped me !!!

 

[thats_me]

Thank youu so much

np

 

[ZainH]

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

Yeah, its a switch operated by an electromagnet.

 

[Moi]

I have a question too.
The brightness of lamps and such...does it depend on current or voltage?
I think it's current, because for example if you have a variable resistor and you up the resistance, the brightness decreases because the current decreases with voltage.
Plus, current is the flow of charges and that's what supplies the energy for the lamp and other appliances.

I believe it's the voltage !
Remeber, is series , the voltages across the bulbs add up to the voltage of the battary. and thus not all bulbs get same brightness
In parallel, voltage is same across all bulbs, thus we get equal brighness and this is one of the advantages of parallel curcuits!!

 

[thats_me]

I have a question too.
The brightness of lamps and such...does it depend on current or voltage?
I think it's current, because for example if you have a variable resistor and you up the resistance, the brightness decreases because the current decreases with voltage.
Plus, current is the flow of charges and that's what supplies the energy for the lamp and other appliances.

i guesss it depends on voltage as its usually stated that lamps in parallel are brighter than in series n in parallel the voltage is max so..

 

[ZainH]

I have a question too.
The brightness of lamps and such...does it depend on current or voltage?
I think it's current, because for example if you have a variable resistor and you up the resistance, the brightness decreases because the current decreases with voltage.
Plus, current is the flow of charges and that's what supplies the energy for the lamp and other appliances.

Funny thing , it's neither and it's both.
POWER determines the brightness of a lamp.
And since Power = current*voltage , it's both x)

 

[ThatReallyReallyWeirdDude]

Funny thing , it's neither and it's both.
POWER determines the brightness of a lamp.
And since Power = current*voltage , it's both x)

That makes sense
Thanks

 

[chaotic]

Thank you

 

[ZainH]

That makes sense
Thanks

The least I could do for the bombardment of chemistry questions I asked xD

 

[ThatReallyReallyWeirdDude]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w09_qp_31.pdf Q9ci the tmprture of metal...HOW ?? asap

ALright temperature rise of water is easy, 1.9*C
The metal is added at 100*C (Question states it's taken from boiling water when it's at the same temp as water, so 100*C)
It will have the same final temperature as the water
so 100-22.9=77.1*C

 

[tribianni]

ohk thnx
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w09_qp_31.pdf Q10c,d,e

 

[areeba fatima]

please help anyone!
what is the difference between the motion of objects falling with and without air resistance?

 

[chaotic]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s11_qp_31.pdf
10 (b)

Need help with the drawing, I don't have the text book, so that's why.

also want the formulas concerning latent heat and heat capacity, thanks.

 

[MERIHAN]

The ray should strike Q and then move to the other end of the optical fibre. There should not be any more reflections.

And:
You will get 1 mark only if you made one more reflection and the lower surface. But you get 0 marks if there is more than 2 reflections.

...

CAN U SHOW IT PLEASE IF POSSIBLE (ONLY A ROUGH DRAWING ) THANK YOU IN ADVANCE

 

[ZainH]

ohk thnx
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_w09_qp_31.pdf Q10c,d,e

For c) Use the equation for power, but you'll have to change it a bit.

Power = energy /time
Energy = power*time
Energy = current*voltage*time
Energy = current^2*resistance*time

NOW you can calcuate it as you have the current, resistance, and time!

ENergy = 2.5^2*3*1
=18.75J

For d) it's easier, just use the formula for power involving current and voltage.
Power= current*voltage
Voltage = power/current
Voltage= 18.75/2
=7.5v

For e) You just subtract the orignial voltage from the one you calculated in part d)!
22000-7.5=21992.5V

 

[ZainH]

please help anyone!
what is the difference between the motion of objects falling with and without air resistance?

WITH air resistance, it's acceleration isn't known..
WITHOUT air resistance, you can straight away tell that it accelerates at 10m/s because the force of gravity is 10 m/s