A galvanometer coil has a resistance of 15 Ω and the metre shows full scale deflection for a current of 4 mA. How will you convert the metre into an ammeter of range 0 to 6 A
Answer & explanation
Correct answer: option 1
$ R_G = 15\Omega$
$\text{Current for which galvanometer shows full scale deflection is i = 4mA.}$
$\text{Range of ammeter is 4 mA, we have to convert this range to 6mA.}$
$\Rightarrow I = 6mA$
$\text{ we need to add a small resistance $R_P$ in parallel to the galvanometer}$
$R_P = \frac{i R_G}{I -i} = 10m\Omega$