X and Y are large,parallel conducting plates close to each other. Each face has an area A. X is given a charge Q. Y is without any charge. Points A, B and C are as shown in the figure then:
This question has multiple correct options
A
the field at B is 2ε0AQ
B
the field at B is ε0AQ
C
the field at A, B and C are of the same magnitude
D
the fields at A and C are of the same magnitude, but in opposite directions
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Updated on : 2022-09-05
Solution
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Correct options are A) , C) and D)
Charge on plate X is Q1=Q and charge on plate Y is Q2=0
Charges on plate surfaces 1 and 4 are q1=q4=2Q1+Q2=2Q
Charge on surface 2 is q2=2Q1−Q2=2Q
and charge on surface 3 is q3=−q2=−2Q
The field at A is EA=E1+E4=2Aϵ0(Q/2)+2Aϵ0(Q/2)=2Aϵ0Q
As both 1 and 4 surfaces have same positive charge so fields at A and C are directed away from the surfaces and have equal magnitude.so are equal in magnitude but opposite in direction.
Thus, EA=2Aϵ0Q (toward left) and EC=2Aϵ0Q (toward right)
Now EB=E2+E3=2Aϵ0Q/2+2Aϵ0Q/2=2Aϵ0Q (toward right) as filled is directed from positive to negative charge.