Biology; Chemistry; Physics: Post your doubts here!

[Nibz]

You always take the absolute values for voltage. It can never be negative. The graph is just to show that the Current is Alternating.

 

[talhajohar]

voltage can be negative in AC.

 

[scouserlfc]

You always take the absolute values for voltage. It can never be negative. The graph is just to show that the Current is Alternating.

YUp i heard that its just convention like that conventional current,but in CIE u will be required to make this plot make sure u see how its done !

 

[Anon]

I got that,

So, as it goes in one direction for half a revolution, and in another, for other half,
It doesnt matter if we start with positive or negative, right? If we are to make a graph..

 

[abcde]

Yes

 

[scouserlfc]

I got that,

So, as it goes in one direction for half a revolution, and in another, for other half,
It doesnt matter if we start with positive or negative, right? If we are to make a graph..

yeah true but for conventions sake u start from positive ! UNLESS STATED THEN U DONT !

 

[scouserlfc]

okay some guidance needed !

(j) state that carbon dioxide and methane are greenhouse gases and may contribute to global warming,
give the sources of these gases and discuss the possible consequences of an increase in global
warming

for this point what will be the points for the answer !
i know flooding,temp rise, what else !


(ii) the use of calcium carbonate to reduce the effect of ‘acid rain’ and in flue gas desulfurisation

and can anybody outline the process involved in this i know what will happen as CACO3 will neutralise the acidic gas just wanna know the process !

Thanks !

 

[Anon]

Source of methane:
-Decay of Vegetative matter
-Intestinal gases of cattles

Carbon di oxide:
-Burning fossil fuel
-Respiration (?)

Effect of Global Warming:

-Melting of Ice caps/ Rise in Sea level (they both are considered one point)
-Desertification
-Extreme Climatic change

 

[scouserlfc]

yeah but this looks hilarious how about plants die due to untolerable temperatures as their enzymes get denatured and they dont make food making all those up the food chain die !

 

[2412957]

Explain why there are approximately equal numbers of babies born of each sex.

 

[VelaneDeBeaute]

B/c the chromosome combinations can be either XX or XY which means there are 50% chances for both a boy and girl to be born!
Thereby, the nbr is approx equal!
Rough explanation though - someone else might provide u details!

 

[2412957]

thank you and do you know how to make a complete genetic diagram with like all the steps including the ratios genotypes and phenotypes

 

[VelaneDeBeaute]

The punnett square? Is that what your talking bout?

 

[2412957]

the other diagram with the genotypes gametes etc

 

[GetSomeLife]

When water reacts with acid HCl, it forms H3O and Chlorine
But wat happens wen it reacts wid Sulphuric acid

 

[GetSomeLife]

Anothr 1 i m lookin fr is:
An acid has the formula of HY or H3Y. How can we know which one is correct by using aqueous solutions of the acid and Sodium Hydroxide. Assume that the concentration of both of them is the same(0.1 mol/dm cube)???

:%) :%)

 

[SalmanPakRocks]

I need help in Thermal Physics (O levels)
Please Define
1)Heat Capacity:
2) Specific Heat Capacity:
3) Latent Heat of Fusion:
4) Specific Latent Heat of Fusion:
5) Latent Heat of Vaporisation:
6) Specific Latent Heat of Vaporisation:
Also if there is any formula for these then do let me know.

 

[sweetiepie]

need formula sheet for physics

density=mass/volume
speed=distance/time
acceleration=change in velocity/time taken
resultant force=mass*acceleration
weight=mass*g
moment= force*perpendicular distance from pivot
spring constant=load/extension
pressure=force/area
pressure in liquid= density*g*depth
kelvin temp= temp in celsius + 273
for a fixed mass of gas at constant temperature: pressure1*volume1=pressure2*volume2
for a fixed mass of gas at constant volume: pressure1/temp1=pressure2/temp2
work=force*distance
gravitational potential energy=mass*height*g
kinetic energy=0.5*m*v^2
specific heat capacity= energy/(mass*temp change)
specific latent heat = energy/mass
power = work done/time
efficiency = energy output/energy input
wave speed = frequency*wavelength
frequency = 1/period
refractive index = speed of light in vacuum/speed of light in medium or (sin*i)/(sin*r)
(sin*critical angle) = 1/refractive index
charge = current*time
resistance=PD/current
total resistance in series: R=R1+R2+R3 (depending on the number of resistors in the series)
total resistance in a parallel circuit: (R1*R2)/(R1+R2)
power=PD*current
energy=PD*current*time
in transformers: output voltage/input voltage = output turns/input turns
in 100% efficient transformers: V1*I1=V2*I2 whereby I is the current!

hope this helps

 

[sweetiepie]

O-Level-Physics-Formula Sheet.pdf

 

[babyy95]

can anyone explain me the difference between a.c and d.c currents?