In a metere bridge, the wire consists of two parts one of length 30 cm and of radius r and the other of radius 2r. Where will the null point occur if the resistance in the left and right gaps are `5Omega` and `8Omega` respectively? The material of the wires is the same.

In a metere bridge, the wire consists of two parts one of length 30 cm

1.	In a metere bridge, the wire consists of two parts one of length 30 cm and of radius r and the other of radius 2r. Where will the null point occur if the resistance in the left and right gaps are `5Omega` and `8Omega` respectively? The material of the wires is the same.
Answer» Correct Answer - 18.3 cm We have `("left gap resistance")/("right gap resistance")=(5)/(8)=0.625` `("left length resistance")/("right length resistance")=((30)/(r^(2)))/((70)/(4r^(2)))=1.7` Hence the null point is on the thin wire. Let it be at a distance x. Then `(5)/(8)=(rhoxx(x))/((pir^(2))/(rhoxx((30-x))/(pir^(2))+(rho70)/(pi4r^(2))))=(4x)/(190-4x)` or `x=18.3cm`

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In a metere bridge, the wire consists of two parts one of length 30 cm and of radius r and the other of radius 2r. Where will the null point occur if the resistance in the left and right gaps are `5Omega` and `8Omega` respectively? The material of the wires is the same.

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