CBSE 2025, Compartment, Set 1

Question

A galvanometer having a coil resistance of $48  \Omega$ shows full-scale deflection for a current of $2.0	ext{ A}$. It can be converted into an ammeter of range $(0-10	ext{ A})$ by connecting : A). in series a resistance of $8 \Omega$ B). in parallel a resistance of $8 \Omega$ C). in parallel a resistance of $12 \Omega$ D). in series a resistance of $12 \Omega$

Edvaya · Accepted Answer

The correct answer is in parallel a resistance of $12 \Omega$. **SOLUTION** To convert a galvanometer into an ammeter, a small shunt resistance ($S$) must be connected in parallel. The formula for the shunt resistance is: $$S = \left(\frac{I_g}{I - I_g}ight) G$$ Given: * Galvanometer resistance, $G = 48 \Omega$ * Full-scale deflection current, $I_g = 2.0	ext{ A}$ * Target current range, $I = 10	ext{ A}$ Substitute the values: $$S = \left(\frac{2.0}{10 - 2.0}ight) 	imes 48$$ $$S = \left(\frac{2}{8}ight) 	imes 48 = \frac{1}{4} 	imes 48 = 12 \Omega$$ Thus, it requires connecting a resistance of **$12 \Omega$ in parallel**.

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Physics > Magnetism Induction And Alternating Current > Moving Charges And Magnetism

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