Q184 / 200 · MHT CET - Medical 2026 (21 April Shift 2) · Physics
An ammeter of resistance $R$ give a full scale deflection when a current of $3\ \text{A}$ passes through it. If it is to measure maximum current of $10\ \text{A}$, the shunt required is
- A$3R/5$
- B$2R/5$
- Correct answerC$3R/7$
- D$4R/7$
Solution
Given, resistance of the ammeter is $R$.
Full scale deflection current, $I_g = 3\ \text{A}$.
Maximum current to be measured, $I = 10\ \text{A}$.
Let the required shunt resistance be $S$.
Since the shunt is connected in parallel with the ammeter, the potential difference across both will be the same.
$I_g R = (I - I_g) S$
$3 \times R = (10 - 3) \times S$
$3R = 7S$
$S = \dfrac{3R}{7}$
Answer: $3R/7$
Full scale deflection current, $I_g = 3\ \text{A}$.
Maximum current to be measured, $I = 10\ \text{A}$.
Let the required shunt resistance be $S$.
Since the shunt is connected in parallel with the ammeter, the potential difference across both will be the same.
$I_g R = (I - I_g) S$
$3 \times R = (10 - 3) \times S$
$3R = 7S$
$S = \dfrac{3R}{7}$
Answer: $3R/7$
Hence, the correct answer is option: 'C'.