Question

In the ac bridge shown in figure the detector D reads zero. Then Z is made of

• A. 50 mH in parallel with $50\Omega$
• B. 50 mH is series with $50\Omega$
• C. 50 nF in series with $10\Omega$
• D. 50 nF in parallel with $5\Omega$

Answer 1

The correct option is B 50 mH is series with $50\Omega$

It is a case of Maxwell's inductance bridge where Z is the (inductance with series resistance).

$L_4=C_1{R}_3{R}_2$

$=100\times {10}^{-9}\times {10}^3\times 500$

$=5\times {10}^{-2}H=50mH$

$R_4{R}_1=R_2{R}_3$

$\therefore R_4=\frac{R_2{R}_3}{R_1}=\frac{500\times 1000}{10\times {10}^3}=50\Omega$