What is the value of unknown resistance R, if galvanometer shows null deflection in the given meter bridge set up ?

Question

What is the value of unknown resistance R, if galvanometer shows null deflection in the given meter bridge set up ? (A) 97.50 Ω (B) 105 Ω (C) 150 Ω (D) 110 Ω

Tardigrade Admin · Accepted Answer

For null deflection in meter bridge (R1/R2)=(l/(100-l)); ∴ (65/R1)=(40/100-40)=(40/60) R1=65×(60/40)=97.5 Ω

Q. What is the value of unknown resistance $R$ , if galvanometer shows null deflection in the given meter bridge set up ?

$97.50 Ω$

$105 Ω$

$150 Ω$

$110 Ω$

For null deflection in meter bridge
$\frac{R _{1}}{R _{2}} = \frac{l}{( 100 - l )}$ ;
$∴ \frac{65}{R _{1}} = \frac{40}{100 - 40} = \frac{40}{60}$
$R_{1} = 65 \times \frac{60}{40} = 97.5 Ω$

Q. What is the value of unknown resistance R, if galvanometer shows null deflection in the given meter bridge set up ?

97.50Ω

105Ω

150Ω

110Ω