If the Wheatstone's bridge with four resistors $R_1, R_2$ and $R_3, R_4$ is balanced, then the correct expression is

• Correct answer
  A

  $\frac{R_2}{R_1}=\frac{R_4}{R_3}$
• B

  $\frac{R_2}{R_3}=\frac{R_1}{R_4}$
• C

  $R_1 R_2=R_3 R_4$
• D

  $R_1+R_2=R_3+R_4$

Solution

For balance condition of Wheatstone bridge, $\frac{R_2}{R_4}=\frac{R_1}{R_3} \quad \text { or } \quad \frac{R_2}{R_1}=\frac{R_4}{R_3}$

Hence, the correct answer is option: 'A'.