# Heat Conduction in Spherical Shell - MCQS with Answers

1. What is the advantage of using the spherical vessel to store fluids at low temperature?

a. heat transfer in sphere is restricted in all direction by insulation
b. sphere has the smallest volume per unit surface area
c. sphere has the largest volume per unit surface area
d. none of the above

ANSWER: c. sphere has the largest volume per unit surface area

2. What is the correct formula for thermal resistance (Rk) of a spherical shell of inner and outer radii as ri and ro respectively and k being the thermal conductivity?

a. Rk= (ri – ro ) / 4 π ri ro k
b. Rk= 4 π ri ro k / (ri – ro )
c. Rk= (ri – ro ) / 4 π k
d. Rk= ri ro / 4 π k (ri – ro )

ANSWER: a. Rk= (ri – ro ) / 4 π ri ro k

3. What is the formula of the thermal resistance for convection at the outer surface of spherical shell of inner and outer radii as ri and ro respectively? Taking ho as convecting heat transfer coefficient of outer fluid.

a. Rc = 4 π ho ro2
b. Rc = 1 / 4 π ho ro2
c. Rc = 4 π ho ro
d. Rc = 1 / 4 π ho ro