Heating Effect of Current and Electrical Measuring Instruments | Physics JEE previous year questions with Solutions

Q 1 :
A galvanometer has a coil of resistance $200 Ω$ with a full scale deflection at $20$ $μ A .$ The value of resistance to be added to use it as an ammeter of range $(0 - 20)$ $m A$ is [2024]

$0.40 Ω$
$0.20 Ω$
$0.50 Ω$
$0.10 Ω$

1

2

3

4

(B) $G = 200$ $Ω$ and $i_{g} = 20$ $μ A$

$i = i_{g} (\frac{G}{S} + 1)$

$\Rightarrow 20 \times 10^{- 3} = 20 \times 10^{- 6} (\frac{200}{S} + 1)$

$\Rightarrow \frac{200}{S} = 999 \Rightarrow S \approx 0.2 Ω$

Q 2 :
A galvanometer of resistance $100 Ω$ when connected in series with $400 Ω$ measures a voltage of up to 10 V. The value of resistance required to convert the galvanometer into an ammeter to read up to 10 A is $x \times 10^{- 2} Ω$ . The value of $x$ is [2024]

800
2
20
200

1

2

3

4

(3)

For voltmeter,

[IMAGE 190]

$i_{g} = \frac{10}{400 + 100} = 20 \times 10^{- 3} A$

for ammeter

[IMAGE 191]

For ammeter

Let shunt resistance $= S$

$i_{g} R = (i - i_{g}) S$

$20 \times 10^{- 3} \times 100 = 10 S \Rightarrow S = 20 \times 10^{- 2} Ω$

Q 3 :
Three voltmeters, all having different internal resistances are joined as shown in figure. When some potential difference is applied across A and B, their readings are $V_{1}$ ?, $V_{2}$ and $V_{3}$ ?. Choose the correct option. [2024]

[IMAGE 192]

$V_{1} = V_{2}$
$V_{1} \neq V_{3} - V_{2}$
$V_{1} + V_{2} > V_{3}$
$V_{1} + V_{2} = V_{3}$

1

2

3

4

(4)

From $KVL, V_{1} + V_{2} - V_{3} = 0 \Rightarrow V_{1} + V_{2} = V_{3}$

Q 4 :
A galvanometer having coil resistance $10 Ω$ shows a full scale deflection for a current of 3 mA. For it to measure a current of 8A, the value of the shunt should be: [2024]

$3 \times 10^{- 3} Ω$
$4.85 \times 10^{- 3} Ω$
$3.75 \times 10^{- 3} Ω$
$2.75 \times 10^{- 3} Ω$

1

2

3

4

(3)

Given $G = 10 Ω, I_{g} = 3 mA and I = 8 A$

In case of conversion of galvanometer into ammeter.

[IMAGE 193]

We have $I_{g} G = (I - I_{g}) S$

$S = \frac{I_{g} G}{I - I_{g}} = \frac{(3 \times 10^{- 3}) \times 10}{8 - 0.003} = 3.75 \times 10^{- 3} Ω$

Q 5 :
The deflection in moving coil galvanometer falls from 25 divisions to 5 divisions when a shunt of $24 Ω$ is applied. The resistance of galvanometer coil will be ____ [2024]

$12 Ω$
$96 Ω$
$48 Ω$
$100 Ω$

1

2

3

4

(2)

Let $x =$ current/division.

Without shunt,

[IMAGE 194]

After applying shunt,

[IMAGE 195]

$Now 5 x \times G = 20 x \times 24$

$G = 4 \times 24 = 96 Ω$

Topic Question Set

Q 1 :
A galvanometer has a coil of resistance $200 Ω$ with a full scale deflection at $20$ $μ A .$ The value of resistance to be added to use it as an ammeter of range $(0 - 20)$ $m A$ is [2024]

Q 2 :
A galvanometer of resistance $100 Ω$ when connected in series with $400 Ω$ measures a voltage of up to 10 V. The value of resistance required to convert the galvanometer into an ammeter to read up to 10 A is $x \times 10^{- 2} Ω$ . The value of $x$ is [2024]

Q 3 :
Three voltmeters, all having different internal resistances are joined as shown in figure. When some potential difference is applied across A and B, their readings are $V_{1}$ ?, $V_{2}$ and $V_{3}$ ?. Choose the correct option. [2024]

[IMAGE 192]

Q 4 :
A galvanometer having coil resistance $10 Ω$ shows a full scale deflection for a current of 3 mA. For it to measure a current of 8A, the value of the shunt should be: [2024]

Q 5 :
The deflection in moving coil galvanometer falls from 25 divisions to 5 divisions when a shunt of $24 Ω$ is applied. The resistance of galvanometer coil will be ____ [2024]

Want Us to Email you About Special Offers & Updates?

Topic Question Set

Q 1 : A galvanometer has a coil of resistance 200Ω with a full scale deflection at 20 μA. The value of resistance to be added to use it as an ammeter of range (0-20) mA is [2024]

Q 2 : A galvanometer of resistance 100Ω when connected in series with 400Ω measures a voltage of up to 10 V. The value of resistance required to convert the galvanometer into an ammeter to read up to 10 A is x×10-2Ω. The value of x is [2024]

Q 3 : Three voltmeters, all having different internal resistances are joined as shown in figure. When some potential difference is applied across A and B, their readings are V1?, V2 and V3?. Choose the correct option. [2024] [IMAGE 192]

Q 4 : A galvanometer having coil resistance 10Ω shows a full scale deflection for a current of 3 mA. For it to measure a current of 8A, the value of the shunt should be: [2024]

Q 5 : The deflection in moving coil galvanometer falls from 25 divisions to 5 divisions when a shunt of 24Ω is applied. The resistance of galvanometer coil will be ____ [2024]

Want Us to Email you About Special Offers & Updates?

Q 1 :
A galvanometer has a coil of resistance $200 Ω$ with a full scale deflection at $20$ $μ A .$ The value of resistance to be added to use it as an ammeter of range $(0 - 20)$ $m A$ is [2024]

Q 2 :
A galvanometer of resistance $100 Ω$ when connected in series with $400 Ω$ measures a voltage of up to 10 V. The value of resistance required to convert the galvanometer into an ammeter to read up to 10 A is $x \times 10^{- 2} Ω$ . The value of $x$ is [2024]

Q 3 :
Three voltmeters, all having different internal resistances are joined as shown in figure. When some potential difference is applied across A and B, their readings are $V_{1}$ ?, $V_{2}$ and $V_{3}$ ?. Choose the correct option. [2024]

[IMAGE 192]

Q 4 :
A galvanometer having coil resistance $10 Ω$ shows a full scale deflection for a current of 3 mA. For it to measure a current of 8A, the value of the shunt should be: [2024]

Q 5 :
The deflection in moving coil galvanometer falls from 25 divisions to 5 divisions when a shunt of $24 Ω$ is applied. The resistance of galvanometer coil will be ____ [2024]