Question

A galvanometer of 100 $ \Omega $ resistance gives full scale deflection with 0.01 A current. How much resistance should be connected to convert it into an ammeter of range , 10 A :

• A. 0.1 $ \Omega $ in parallel
• B. 0.1 $ \Omega $ in series
• C. 0.2 $ \Omega $ in parallel
• D. 0.2 $ \Omega $ is series

Answer 1

Answer: (A)

Here: resistance of galvanometer $ G=100\,\Omega $ Maximum current across galvanometer $ {{I}_{g}}=0.01A $ Current range in ammeter = 10 A Since, the shunt resistance should be connected in parallel to convert the galvanometer into an ammeter. $ S=\left( \frac{{{I}_{g}}}{I-{{I}_{g}}} \right)G=\left[ \frac{0.01}{(10-0.01)} \right]\times 100 $ $ =0.1\,\Omega $