# Physics

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We have an infinite, non-conducting sheet of negligible thickness carrying a uniform surface charge density +σ=7.00e-6 C/m2 and, next to it, an infinite parallel slab of thickness D=17 cm with uniform volume charge density ρ=−4.94e-5 C/m3 (see sketch). Note that the slab has a negative charge. All charges are fixed in place and cannot move.

Reminder: The "x.xxenn C/m2 and C/m3" notations for σ and ρ, respectively, mean "x.xx×10nn C/m2 and C/m3".

Assuming the infinite sheet is in the x-y plane, and zˆ points as shown in the figure, calculate the components of the electric field at the locations listed below. Since we do not ask for the direction separately, these components could be positive or negative.

(a) a distance h=4 cm above (i.e. in the +zˆ direction) the positively charged sheet.
Ex

Ey

Ez

(b) inside the slab at a distance d=4 cm below (i.e. in the −zˆ direction) the positively charged sheet. Note that d<D so that this is also a distance 13 cm above the bottom of the slab.
Ex

Ey

Ez

(c) a distance H=29 cm below (i.e. in the −zˆ direction) the charged sheet. Note that H>D so that this is also a distance 12 cm below the bottom of the slab.

Ex

Ey

Ez

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a) 0
0
sigma/(2*epsilon_0) - rho*D/(2*epsilon_0)

b)
0
0

c)
0
0

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what about c part 3 and b part 3???

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c part 3)
-sigma/(2*epsilon_0)-rho*(D-
d)/(2*epsilon_0) +rho*d/(2*epsilon_0)

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sry it was b part 3)

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demon, any help with the capacitor brushes problem?

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anyone for question 7

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a) (sigma/(2*epsilon_0))-(rho*D/(2*epsilon_0))

c)-sigma/(2*epsilon_0)+(rho*D/(2*epsilon_0))

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b) -sigma/(2*epsilon_0)-rho*(D-
d)/(2*epsilon_0) +rho*d/(2*epsilon_0)

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Please question 7, 9, 10 and 11.

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anyone for 8

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Please 7, 9, 10 and 11.

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7) a) lambda/0.5
b) lambda/0.125

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For Inductor
a: I=0 A
b: (Supply Voltage/R)*(1-e^(-Rt/L))
c: see above (put the value of t in sec

For Capacitor
Use v(t)=Supply Voltage*(1-e^(-t/RC))
Divide the above answer by R to get the Current

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question 9
a: Ec1=Voltage/plate separation
b: because the battery is connected the E field does not change

c: when the battery is disconnected then
Q1+Q2 must equal Q1'+Q2'
Ec1=Q1'/(k*C1*d) and Ec2=Q2'/(C2*d)
where Q1'=(Q1+Q2)/(1+(C2/K*C1)
and Q2'=C2/(K*C1)*(Q1+Q2)/(1+(C2/K*C1))