Question

A galvanometer of resistance$70 \Omega$, is converted to an ammeter by a shunt resistance. The value of its resistance will become

• A. $0.025 \Omega$
• B. $0.022 \Omega$
• C. $0.035 \Omega$
• D. $0.030 \Omega$

Answer 1

Answer: (D)

$0.030 \Omega$

Answer 2

$\mathrm { R } = \frac { \mathrm { R } _ { \mathrm { G } } \mathrm { r } _ { \mathrm { s } } } { \mathrm { R } _ { \mathrm { G } } + \mathrm { r } _ { \mathrm { s } } }$

Here $\mathrm { R } _ { \mathrm { G } } = 70 \Omega , \mathrm { r } _ { \mathrm { s } } = 0.03 \Omega$

$\therefore \mathrm { R } = \frac { 70 \times 0.03 } { 70 + 0.03 } = 0.02998 = 0.03 \Omega$