ICSE − Q & A

explain "critical angle of diamond is 24"

WORKING OF THE CRT
Loads of people have trouble understanding this so I thought I'd help make it a little simpler :] 

1) Filament heats the Cathode. 
2) Cathode gets charged and emits the electrons
3) Grid(situated between Anode and Cathode) directs the entry of electrons
4) Anode provides Kinetic energy to the electrons
5) Deflecting plates direct the electrons to the flourascent screen. 

This is the process of how an electrical signal is converted into a visual signal. Please correct me if I made any mistake. 
Hope I helped :]

Suresh applies a force of 6kgf to draw a 4.8kg bucket of water from a well using a single fixed pulley. Assuming all extra force is used to overcome frictional forces, calculate MA, VR, eff.
ans should be 0.8 MA, VR is 1 and eff. 80% right?

I have a question that my friend asked me:
Consider two heating devices A and B which use a wire of high resistance to produce heating effect.
Let the Resistance of A be x and that of B be 2x
So B should produce more heat.(as the resistance of wire is double)
But V = IR(so I is inversely proportional to R)
So let the current in A be y, so the current in B should be y/2
According to H = I^2RT
Heat produced is directly proprtional to the SQUARE of I(current)
So the heat produced by B must be less than that by A.
Which heater produces more heat?

what is the exact meaning of power rating ?

how to find ratio of wavelengths?

Is there any particular direction for the deflection of the magnet in Oersted's experiment and also does the deflection depend on which side of conductor the north Pole faces and the south Pole faces or the way the magnet us kept?

What is wrong in 2016 edition Selina Phy tb? Can any one tell me and correct it?

A water pump raises 50 litres of water through a height of 25 m in 5 s. Calculate the power which the pump supplies. [Take g = 10 Nkg-1 and density of water = 1000kgm-1]

PLEASE SOLVE THIS

Hey , a bulb is rated 100w , 250v . what does it convey?
and ,,, The critical angle of glass is 42 degrees
ASAP, Thank you in advance :)