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Question
The capacitance between adjacent plates shown in Fig 20.95(a) is 50 nF. A1μC charge is placed on the middle plate. Find the charge on the outer surface of upper plate and the potential difference between upper and middle plates:
The capacitance between adjacent plates shown in Fig 20.95(a) is 50 nF. A1μC charge is placed on the middle plate. Find the charge on the outer surface of upper plate and the potential difference between upper and middle plates:
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Solution
The correct option is A 0.5μC,10V
The charge distribution on the plates is shown in figure below.
As the field inside plate at p is zero so 12Aϵ0[−q1+q+1−q2−q2+q3−q3]=0
or 2q2=1⇒q2=0.5μC
Here q1=−(1−q2)=−(1−0.5)=−0.5μC
Thus charge on outer surface of upper plate is −q1=0.5μC
The potential difference between upper and middle plates is V=q1V=0.5×10−650×10−9=10V
The charge distribution on the plates is shown in figure below.
As the field inside plate at p is zero so 12Aϵ0[−q1+q+1−q2−q2+q3−q3]=0
or 2q2=1⇒q2=0.5μC
Here q1=−(1−q2)=−(1−0.5)=−0.5μC
Thus charge on outer surface of upper plate is −q1=0.5μC
The potential difference between upper and middle plates is V=q1V=0.5×10−650×10−9=10V
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