Find the volume of a sphere of radius a.

Answer

A, C

Explanation

`a=r_1=5cm 0.05 m,`
`b=r_2=20cm =10^(2)C.`
Now considering a small strip of thickness `dr` at a distance 'r'
`A=4 pi (r_2)`
`H=(-4 pi (r-_2)ld theta)/(dr)`
`-ve because as 'r' increases 'Q' decreases `
`int_(a)^(b)(dr)/(r^(2)= (-4 pi K)/(H) int_(a)^(b) d theta`
on integration H=(dQ)/(dt)=K(4 pi ab(theta_1-theta_2))/(b-a)`
`Putting the values we get `
`(Kxx4xx3.14xx5xx20xx40xx10^(-3))/(15xx10^(-2))=100`
`K=(15)/(4xx3.14xx4xx10^(-1))`
`=2.985=3W//m-^(@)C.`