Consider a circular as shows in Fig. `6.5` (a). We want to measure the current `i` flowing in the circuit.

For this we connect an ammeter of resistance `R_(A)` as shows in Fig. `6.5`(b). Find the percentage error in the current.

Explanation

Actual current is `I = E//R`. Let the current measured by the ammeter be `i_(i)`, then `i_(i) = E//(R + R_(A))`, clearly `L_(i)` is less than `i`. Percentage error is
`(I - i_(i))/(i) xx 100 = ((E//R - E//(R + R_(A)))/(E//R)) xx 100 ((R_(A))/(R + R_(A))) xx 100`