Which of the following is  closer to a black body ?

Variation of radiant energy emitted by sun, filament of tungsten lamp and welding arc as a function of its wavelength is shown in figure. Which of the following options is the correct match ?

       

Three disc A, B and C having radii 2 m, 4 m and 6 m respectively are coated with carbon black on their outer surfaces. The wavelengths corresponding to maximum intensity are 300 nm, 400 nm and 500 nm respectively. The powers radiated  are Q_A, Q_B and Q_C respectively.

The volume of a liquid is 830 m³ at 30^o C and it is 850 m³ at 90^o C.  The coefficient of volume expansion of the liquid is 

The temperature coefficient of resistance of a wire is 0.00125^oC^-1. At 300 K, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at which temperature ?

540 g of ice at 0^o C is mixed with 540 g of water at 80^o C.  The final temperature of the mixture is

In which of the following processes, convection does not take place primarily ?

The unit of Stefan's constant is :

A copper block of mass 2.5 kg is heated in a furnace to a temperature of 500^o C and then placed on a large ice block.  The maximum amount of ice that can melt is :
(sp.heat of Cu = 0.39 J/gm/^o C and heat of diffusion of water = 335 J/gm)

Two spheres of the same material have radii 1 m and 4 m and temperatures 4,000 K and 2,000 K respectively. The ratio of the energy radiated per second by the first sphere to that by the second is: