In the circit shown the three ammeters (marked as 1, 2, 3) are indentical, each have a resistance `R_(0) = 2Omega`. Between points A and B three is a constant potential difference of 19V. The first and second ammeter read `I_(1)=2.5" A and "I_(2)=1.5 A`respectively.
(a) What is the reading of third ammeter ?
(b) Calculate value of resistance R.
( c) Investigate what happens to current `I_(3)` if the value of `R_(x)` is changed. Show approximately graphical variation of `I_(3)vsR_(x)`.
Note : Reading of ammeter implies current through brance of ammeter.

Answer

(a) 1A,
(b) `4 Omega" "I_(3)=(V(R_(x)-R))/((2R_(0)+3R)R_(x)+R_(0)(R_(0)+2R))`
`(##RES_PHY_CE_E03_065_A01##)`
The graph of the function is a hyperbola. Its special points are : at `R_(x)=0I_(3)=-3.8A;` at `R_(x) ; = 4I_(3)=0;` at `R_(x)=32Omega I_(3)=1A ; ` If `R_(x)to oo, I_(3)" tends to 19/16=1.1875 A"`.