Question

Resistance of $12\Omega$ and $X\Omega$ are connected in parallel in the left gap and resistances of $9\Omega$ and $7\Omega$ are connected in series in the right gap of the meter bridge. If the balancing length is 36 cm, then the value of resistance X is

• A. $72\Omega$
• B. $54\Omega$
• C. $36\Omega$
• D. $64\Omega$
• E. $32\Omega$

Answer 1

The correct option is C $36\Omega$

The equivalent resistance for left gap is $L=\frac{12X}{12+X}$ and the equivalent resistance for right gap is $R=9+7=16\Omega$

The balanced condition of a meter bridge : $\frac{L}{R}=\frac{l_L}{l_R}$

or $\frac{12X}{(12+X)16}=\frac{36}{64}$

or $X=36\Omega$