Question

A galvanometer having a coil resistance of $30\Omega$ shows full scale defection when a current of $2A$ passes through it. It can be converted into an ammeter to read currents upto $10A$ by :

• A. by putting in series a resistance of $240\Omega$ .
• B. by putting in parallel a resistance of $240\Omega$ .
• C. by putting in series a resistance of $7.5\Omega$ .
• D. by putting in parallel a resistance of $7.5\Omega$ .

Answer 1

Answer: (D)

$S=\frac{I_{g} R_{g}}{I-I_{q}}=\frac{(2)(30)}{10-2}=\frac{2 \times 30}{8}=\frac{15}{2}=7.5 \Omega$