The resistance of ammeter is `R_(0)`

Options

A. If `r=0`, if the value of resistance `R` increase, the current in ammeter will remain same
B. If `r=0`, if the value of resistance `R` decrease, the current in ammeter will remain same
C. If `r!=0`, if `R` increase, the current in ammeter will remian same
D. If `r!=0`, if `R` increases, the current in ammeter will increase

Answer

A

Explanation

`r=0`

`i_(0) = V//R_(0), i^(') = V//R`
`i_(0)` remains same whether `R` is increased or decreased
`r != 0`

When `R` is increased, equivalent resistance of `R_(0)` and `R` increase, hence equivalent resistance of circuit increase. the current supplied by battery ie. `i_(1)` decreases, p.d. across ammeter i.e., `(V =i_(1)r)` increases and hence current in ammeter.
`i_(0)^(') = (V-i_(1)r)/(R_0)`, increases.