Saturday, 21 November 2015

homework and exercises - Wheatstone bridge Capacitor,Dead Capacitor



Wheatstone bridge Capacitor,Dead Capacitor


I want to know that if in a Wheatstone Bridge ,that is made of capacitors only we have this condition c1c3=c2c4.


The c5 capacitor would be dead and it's voltage would be zero? Actually I am looking for a mathematical proof.



Answer



Suppose first that C5 is absent, that the voltage at the connection point of C2 and C3 is zero and that of the connection point of and C4 is V(ω). The impedance of a capacitor C at the angular frequency ω is


Z(C)=1iωC.



Then V(A)=Z(C2)Z(C1)+Z(C2)V(ω)=1Z(C1)Z(C2)+1V(ω),V(B)=Z(C3)Z(C3)+Z(C4)V(ω)=1Z(C4)Z(C3)+1V(ω).

If V(A)=V(B) then attaching C5 does not change the situation since there is no voltage across it. But V(A)=V(B)Z(C1)Z(C2)=Z(C4)Z(C3)


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