1. What is the energy stored in the 9.1 F capacitor of a heart defibrillator cha

Question

1. What is the energy stored in the 9.1 F capacitor of a heart defibrillator charged to 10.6 kV?

2. What is the potential 0.44×10-10 m from a proton (the average distance between the proton and electron in a hydrogen atom)?

3. An evacuated tube uses an accelerating voltage of 14 kV to accelerate electrons to hit a copper plate and produce x rays. Non-relativistically,what would be the maximum speed of these electrons? Give answer in terms of 108 m/s.

4. An electrostatic paint sprayer has a 0.3 m diameter metal sphere at a potential of 11 kV that repels paint droplets onto a grounded object. What charge is on the sphere? Give answer in terms of 10-7 C.

Explanation / Answer

1.

Energy stored in capacitor is given by:

U = 0.5*C*V^2

Using given values:

U = 0.5*9.1*10^-6*(10.6*10^3)^2

U = 511.24 J

B.

Electric potential is given by:

V = kQ/r

Q = e = 1.6*10^-19 C

r = 0.44*10^-10 m

V = 9*10^9*1.6*10^-19/(0.44*10^-10)

V = 32.73

3.

Using energy conservation

dKE = dPE

0.5*m*V^2 = q*dV

V = sqrt (2*q*dV/m)

V = sqrt (2*1.6*10^-19*14*10^3)/(9.1*10^-31))

V = 7.016*10^7 m/sec

V = 0.702*10^8 m/sec

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