- #1
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problem #1
Two point charges of +3.0uC and -7.0uC are placed at x=0 and x=.20m, respectively. What is the magnitude of the electric field at the point midway between them (x=.10m)?
E3 = (kq)/r^2 = [(9x10^9 )(3x10^-6 C)]/.10m^2 = 2.7x10^6 N/C
E7 = (kq)/r^2 = [(9x10^9 )(7x10^-6 C)]/.10m^2 = 6.3x10^6 N/C
E=E3+E7 = 9x10^6 N/C
solutions manual has the answer as 9x10^5 N/C
problem #2
If the distance between two closely spaced parallel planes is halved, the electric field between them: becomes 4 times as large.
E=4/A
E=4/d^2
if d=2, E=1
if d=1, E=4
so becomes 4 times as large
solutions manual has the answer as remains the same
problem #3
A 12-V battery is connected to a parallel-plate capacitor with a plate area of 0.40 m^2 and a plate separation of 2.0 mm. How much energy is stored in the capacitor?
A=0.40 m^2
d=2.0 mm = .002 m
V= 12V
find Uc
C=(EoA)/d = (8.85x10^-12 x .40 m^2)/.002 m
C= 1.77x10^-9 F
Uc=1/2cv^2 = 1/2(1.77x10^-9 F)(12v)^2 = 1.27x10^-7 J
solutions manual has the answer as 2.5x10^-7 J
Two point charges of +3.0uC and -7.0uC are placed at x=0 and x=.20m, respectively. What is the magnitude of the electric field at the point midway between them (x=.10m)?
E3 = (kq)/r^2 = [(9x10^9 )(3x10^-6 C)]/.10m^2 = 2.7x10^6 N/C
E7 = (kq)/r^2 = [(9x10^9 )(7x10^-6 C)]/.10m^2 = 6.3x10^6 N/C
E=E3+E7 = 9x10^6 N/C
solutions manual has the answer as 9x10^5 N/C
problem #2
If the distance between two closely spaced parallel planes is halved, the electric field between them: becomes 4 times as large.
E=4/A
E=4/d^2
if d=2, E=1
if d=1, E=4
so becomes 4 times as large
solutions manual has the answer as remains the same
problem #3
A 12-V battery is connected to a parallel-plate capacitor with a plate area of 0.40 m^2 and a plate separation of 2.0 mm. How much energy is stored in the capacitor?
A=0.40 m^2
d=2.0 mm = .002 m
V= 12V
find Uc
C=(EoA)/d = (8.85x10^-12 x .40 m^2)/.002 m
C= 1.77x10^-9 F
Uc=1/2cv^2 = 1/2(1.77x10^-9 F)(12v)^2 = 1.27x10^-7 J
solutions manual has the answer as 2.5x10^-7 J