A capacitor is formed from two concentric spherical conducting shells separated

Question

A capacitor is formed from two concentric spherical conducting shells separated by vacuum. The inner sphere has radius 11.0 cm, and the outer sphere has radius 14.5 cm. A potential difference of 140 V is applied to the capacitor What is the energy density at 11.1 cm . Just outside the inner sphere? 1.8 10-8 Im Submit My Answers Give Up Incorrect; Try Again; 6 attempts remaining Part B What is the energy density at r 14.4 cm, just inside the outer sphere? | u= 4.7. 10-7 Im Submit My Answers Give Up Incorrect; Try Again; 6 attempts remaining

Explanation / Answer

Energy density= 1/2**E^2 = 1/2*0*[Q/40r2] = Q/80r2--------------(1)

Q=CV----------------(2)

C= 40/[1/R1 -1/R2] ----------------(3)

Combing above three eqns,

Energy density= {4V0/[1/R1 -1/R2]}/{80r2} = V/[2r2(1/R1 -1/R2)] ---------------(4)

a)

Plug values given

R=0.111

Energy density = 140/[(2*0.11^2(1/0.11-1/0.145)] = 2636.36 J

b)

Plug values given

r=0.144

Energy density = 140/[(2*0.14.4^2(1/0.11-1/0.145)] = 1538.39 J

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