GG...Ur awesome 
I have few more doubts 
In first Q..Why is the answer D? 
The last two Qs are of the same sort, just need a basic explanation.
Thanks Alot 
It'll take me time to type all my answers so I hope you have patience.
EDIT : I don't get the first one and the last one :S
my answer for the second Question is as follows ;
Lamp As the temperature increases , the atoms vibrate violently .
flow of charge is blocked by the vibrating atoms.
the flow of charge decreases and ,since the flow of charges is directly proportional to the current , the
current decreases hence the
resistance increases Thermistor As temperature increases , the electrons gain Kinetic energy and they hit the lattice atoms and the flow of charges increases , and since the flow of charges is directly proportional to the current , the c
urrent increases and hence the
resistance decreases EDIT :
for the First Question
Thanks to
Master_Key ;
Divide the current into two parts. Like if 3 A Max.
then 1A for R
and 2A for R1+R2.
P = I2R
For P of R
P = 12R
For P of R1+R2
P = 22R1 or R2
P in R1 and R2 are same
Ratio is
1 : 4.or Conside R and R1+R2 in parallel.
Take V as a fixed V. In parallel circuits, V is always same.
P = V2/R
For P of R
P = V2/R
For P of R1+R2
P = V2/(R1+R2)
and find the ratio.
EDIT again
Question 3.
I = nAqv where
I = current
n = charge carrier density
q = charge of an electron
v = drift speed
Increase in temperature decreases the resistance of Thermistor.
The increase in temperature causes an increase in drift velocity, so current increases if voltage is to remain same. That explains I against V graphs that defy Ohm's law (which would predict a straight line) for thermistor.
hope i helped.
MORE HELP FOR PHYSICS FROM HERE.
resources.r9paul.org/ASA2/Physics/AS_RevisionBook.pdf
