In the circuit shown in figure the reading of ammeter is the same with both switches open as with both closed. Then find the resistance `R`. (ammeter is ideal).

Options

A. `550 Omega`
B. `400 Omega`
C. `350 Omega`
D. `600 Omega`

Answer

D

Explanation

(d) Current with both switches opened is
`(V)/(R_(eq)) = (1.5)/(450) = (1)/(300) = i`
After closing the switch `V_(1) + V_(2) = V`
`(1)/(3) + V_(2) = (3)/(2) implies V_(2) = (9 - 2)/(6) = (7)/(6)`
`I = (7)/(800)` By Kirchhoff's first law
`i_(2) = (7)/(1800) = (1)/(300) = (1)/(1800) , i_(2) R = i_(1) R_(2)`
`R = 1800 ((1)/(3)) = 600 Omega`