Question

In a balanced meter bridge, the segment of wire opposite to a resistance of $70\, \Omega$ is $70\, cm$. The unknown resistance is

• A. $30\, \Omega$
• B. $60\, \Omega$
• C. $90\, \Omega$
• D. $15\, \Omega$

Answer 1

Answer: (A)

In balanced meter bridge known resistance,
$S=70\, \Omega, l=70\, cm$
$\therefore $ Unknown resistance,
$R=S\left(\frac{100-l}{l}\right)=\frac{70(100-70)}{70}$
$=30\, \Omega$