SATHEE: Moving Charges and Magnetism

Moving Charges and Magnetism - Result Question 80

82. A galvanometer of resistance $50 Ω$ is connected to battery of $3 V$ along with a resistance of $2950 Ω$ in series. A full scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be

(a) $5050 Ω$

(b) $5550 Ω$

(d) $4450 Ω$

[2008]

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Answer:

Correct Answer: 82. (d)

Solution:

(d) Total internal resistance $= (50 + 2950) Ω$ $= 3000 Ω$

Emf of the cell, $ε = 3 V$

$∴$ Current $= \frac{ε}{R} = \frac{3}{3000} = 1 \times 10^{- 3} A = 1.0 m A$

$∴$ Current for full scale deflection of 30 divisions is $1.0 m A$ .

$∴$ Current for a deflection of 20 divisions,

$I = (\frac{20}{30} \times 1) m A$ or $I = \frac{2}{3} m A$

Let the resistance be $x Ω$ . Then

$x = \frac{ε}{I} = \frac{3 V}{(\frac{2}{3} \times 10^{- 3} A)} = \frac{3 \times 3 \times 10^{3}}{2} Ω$

$= 4500 Ω$

But the resistance of the galvanometer is $50 Ω$ .

$∴$ Resistance to be added

$= (4500 - 50) Ω = 4450 Ω$

Moving Charges and Magnetism - Result Question 80

82. A galvanometer of resistance $50 Ω$ is connected to battery of $3 V$ along with a resistance of $2950 Ω$ in series. A full scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be

Answer:

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Moving Charges and Magnetism - Result Question 80

82. A galvanometer of resistance 50Ω is connected to battery of 3V along with a resistance of 2950Ω in series. A full scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be

Answer:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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82. A galvanometer of resistance $50 Ω$ is connected to battery of $3 V$ along with a resistance of $2950 Ω$ in series. A full scale deflection of 30 divisions is obtained in the galvanometer. In order to reduce this deflection to 20 divisions, the resistance in series should be