ALL PHYSICS DOUBTS - POST HERE !!

[thenewkid™]

0625/32/M/J/09  ques 7 b pleazz
i noe de fact dat evaporation is a coollin effect
bt dint gt de othr parts of ms!!!!!!

the cloth always remains damp because it is dipped in water on  both side
the energy required for the molecules to evaporate is obtained from the milk
hope this helps

[Adzel]

Can someone please explain the whole concept of the LDR for me pleasee?? It's quite confusing.

The animation shows that when the torch is turned on, the resistance of the LDR falls, allowing current to pass through it.

[Weaam]

Can anyone tell me what monochromatic light is??
Really Urgent!!

[Ghost Of Highbury]

Can anyone tell me what monochromatic light is??
Really Urgent!!

Light of a single frequency.

[NightHawkerr]

LDR :

As Light intensity decreases on LDR, The resistance across it increases, thus V input increases. When V input is more than 0.6 V, the transistor is switched ON, and thus the lamp/ alarm etc. turns ON.

[SuperGenius]

the light which made of only one kind of wavelength of electromagnetic waves.
hope you can understand my english

[Ivo]

Light of a single frequency.

Or just light of one colour!

[Weaam]

Light of a single frequency.

Thaaaaank yooou!

[thenewkid™]

monochromatic light is light of the same colour and wavelength
(different colors hv different wavelengths)

[NightHawkerr]

Hey one question, A box full of matches.. Does it have internal(thermal) energy or chemical energy?

[rhea]

@ rhea:

The function of a slip ring is to make one or more continuous electrical connections from points in a stationary unit to points in a rotating section. Electrical connections on slip rings can be for both power and data signal connections.

hey thanks =)

just another doubt:

Ac generator/ DC motor, which one takes half-turns?

[Vin]

Hehe yeah a pendin Q  

http://www.freeexampapers.us/IGCSE/Physics/CIE/2009%20Nov/0625_w09_qp_32.pdf

Q9 part c all  

9 c)i)
ok so the initial temperature of water was 21.1 which rose to 22.9 so the diff. = 22.9-21.1 = 1.8*C
Initial temperature of metal was 100*C and it fell to 22.9*C .. y 100 because it was taken out from boiling water which is 100*C
so diff. = 100 - 22.9 = 77.1*C

ii) Thermal energy(Q) = mass * specific heat capacity * temp. change

= 0.2kg * 4200 J / (kg K) * 1.8*C
= 1512 J

iii) Heat lost by water  = heat gained by metal
Q = 1512 J
m = 0.05kg
temp.change = 77.1*C

Q = mc(theta)
c = Q/m(theta)

c = 1512/0.05*77.1

  = 392.22
  =392 J/kg*C

iv) Heat lost in surroundings

[rhea]

Hey one question, A box full of matches.. Does it have internal(thermal) energy or chemical energy?

chemical, i guess.

[Adzel]

hey thanks =)

just another doubt:

Ac generator/ DC motor, which one takes half-turns?

Split rings = half turns = DC motor

[thenewkid™]

Hey one question, A box full of matches.. Does it have internal(thermal) energy or chemical energy?

chemical energy

sry didnt notice u ppl hd answered