9. +-/10 points Two point charges Q1 = +5.20 nC and Q2 =-2.00 nC are separated b

Question

9. +-/10 points Two point charges Q1 = +5.20 nC and Q2 =-2.00 nC are separated by 25.0 cm. (a) What is the electric potential at a point midway between the charges? (b) What is the potential energy of the pair of charges? What is the significance of the algebraic sign of your answer? Positive work must be done to separate the charges. Negative work must be done to separate the charges Submit Answer Save Progress 4. -10 points A parallel-plate capacitor has capacitance 6.00 F (a) How much energy is stored in the capacitor if it is connected to a 15.00-V battery? (b) If the battery is disconnected and the distance between the charged plates doubled, what is the energy stored? c) The battery is subsequently reattached to the capacitor, but the plate separation remains as in part (b). How much energy is stored? Submit Answer Save Progress

Explanation / Answer

a)

AT midpoint,

r1=r2 = 25.0/2 = 12.5 cm = 0.125 m

V = K*[Q1/r1 + Q2/r2]

V = (9*10^9)*[(5.20*10^-9)/0.125 + (-2.00*10^-9)/0.125]

V = (9*10^9)*[4.16*10^-8 -1.60*10^-8]

V = (9*10^9)*(2.56*10^-8)

V = 230 V

Answer: 230 V

b)

r = 25.0 cm = 0.250 m

PE = K*Q1*Q2/r

= (9*10^9)*(5.20*10^-9)*(-2.00*10^-9)/(0.250)

= - 3.74*10^-7 J

Answer: - 3.74*10^-7 J

c)

negative sign shows that

positive work must be done to separate charges

I am allowed to answer only 1 question at a time

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