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,

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

for ammeter

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]

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

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.

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,

After applying shunt,

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

$G = 4 \times 24 = 96 Ω$

Q 6 :
A galvanometer has a resistance of 50 Ω and it allows maximum current of 5 mA. It can be converted into voltmeter to measure upto 100 V by connecting in series a resistor of resistance [2024]

5975 $Ω$
20050 $Ω$
19950 $Ω$
19500 $Ω$

1

2

3

4

(3)

$= 20000 - 50 = 19950 Ω$

Q 7 :
In an ammeter, 5% of the main current passes through the galvanometer. If resistance of the galvanometer is G, the resistance of ammeter will be [2024]

$\frac{G}{20}$
$\frac{G}{199}$
$199$ $G$
$200$ $G$

1

2

3

4

(1)

By using KVL

$I_{g} \cdot G = I_{S} \cdot S$

$S = \frac{I_{g} G}{I_{S}} = \frac{\frac{5}{100} I_{0}}{\frac{95}{100} I_{0}} G = \frac{1}{19} G$

$R_{A} = \frac{S G}{S + G} = \frac{\frac{G}{19} \cdot G}{\frac{G}{19} + G} = \frac{G^{2}}{\frac{19 \times 20 G}{19}} = \frac{G}{20}$

Q 8 :
In the given figure an ammeter A consists of a 240 $Ω$ coil connected in parallel to a 10 $Ω$ shunt. The reading of the ammeter is ______________ mA. [2024]

0%

(160)

$R_{A} = \frac{G \cdot S}{G + S} = \frac{240 \times 10}{240 + 10} = \frac{240}{25} Ω = 9.6 Ω$

$R_{eq} = 140.4 + 9.6 = 150 Ω$

$\Rightarrow I = \frac{24}{150} = 160 mA$

Q 9 :
To determine the resistance (R) of a wire, a circuit is designed below. The V−I characteristic curve for this circuit is plotted for the voltmeter and the ammeter readings as shown in figure. The value of R is .......... $Ω$ . [2024]

0%

(2500)

The resistance of the circuit, $R_{net} = \frac{V}{I} = \frac{4}{2 mA} = 2 \times 10^{3} Ω$

Equivalent resistance, $\frac{10^{3} \times 10 R}{10^{4} + R} = 2 \times 10^{3}$

$10^{4} R = 2 \times 10^{7} + 2 \times 10^{3} R$

$\Rightarrow R = \frac{10^{4}}{4} Ω = 2500 Ω$

Q 10 :
In the given circuit, the current flowing through the resistance 20 $Ω$ is 0.3 A, while the ammeter reads 0.9 A. The value of $R_{1}$ is ________ $Ω$ . [2024]

0%

(30)

Given, $i_{1} = 0.3 A,$ $i_{1} + i_{2} + i_{3} = 0.9 A$

So, $V_{A B} = i_{1} \times 20 Ω = 20 \times 0.3 V = 6 V$

$i_{2} = \frac{6 V}{15 Ω} = \frac{2}{5} A$

$i_{1} + i_{2} + i_{3} = \frac{9}{10} A$

$\frac{3}{10} + \frac{2}{5} + i_{3} = \frac{9}{10} \Rightarrow i_{3} = 0.2 A$

$\Rightarrow (0.2) R_{1} = 6$

$\Rightarrow R_{1} = \frac{6}{0.2} = 30 Ω$

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]

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]

Q 6 :
A galvanometer has a resistance of 50 Ω and it allows maximum current of 5 mA. It can be converted into voltmeter to measure upto 100 V by connecting in series a resistor of resistance [2024]

Q 7 :
In an ammeter, 5% of the main current passes through the galvanometer. If resistance of the galvanometer is G, the resistance of ammeter will be [2024]

Q 8 :
In the given figure an ammeter A consists of a 240 $Ω$ coil connected in parallel to a 10 $Ω$ shunt. The reading of the ammeter is ______________ mA. [2024]

0%

Q 9 :
To determine the resistance (R) of a wire, a circuit is designed below. The V−I characteristic curve for this circuit is plotted for the voltmeter and the ammeter readings as shown in figure. The value of R is .......... $Ω$ . [2024]

0%

Q 10 :
In the given circuit, the current flowing through the resistance 20 $Ω$ is 0.3 A, while the ammeter reads 0.9 A. The value of $R_{1}$ is ________ $Ω$ . [2024]

0%

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]

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]

Q 6 : A galvanometer has a resistance of 50 Ω and it allows maximum current of 5 mA. It can be converted into voltmeter to measure upto 100 V by connecting in series a resistor of resistance [2024]

Q 7 : In an ammeter, 5% of the main current passes through the galvanometer. If resistance of the galvanometer is G, the resistance of ammeter will be [2024]

Q 8 : In the given figure an ammeter A consists of a 240Ω coil connected in parallel to a 10Ω shunt. The reading of the ammeter is ______________ mA. [2024]

0%

Q 9 : To determine the resistance (R) of a wire, a circuit is designed below. The V−I characteristic curve for this circuit is plotted for the voltmeter and the ammeter readings as shown in figure. The value of R is .......... Ω. [2024]

0%

Q 10 : In the given circuit, the current flowing through the resistance 20 Ω is 0.3 A, while the ammeter reads 0.9 A. The value of R1 is ________ Ω. [2024]

0%

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]

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]

Q 6 :
A galvanometer has a resistance of 50 Ω and it allows maximum current of 5 mA. It can be converted into voltmeter to measure upto 100 V by connecting in series a resistor of resistance [2024]

Q 7 :
In an ammeter, 5% of the main current passes through the galvanometer. If resistance of the galvanometer is G, the resistance of ammeter will be [2024]

Q 8 :
In the given figure an ammeter A consists of a 240 $Ω$ coil connected in parallel to a 10 $Ω$ shunt. The reading of the ammeter is ______________ mA. [2024]

Q 9 :
To determine the resistance (R) of a wire, a circuit is designed below. The V−I characteristic curve for this circuit is plotted for the voltmeter and the ammeter readings as shown in figure. The value of R is .......... $Ω$ . [2024]

Q 10 :
In the given circuit, the current flowing through the resistance 20 $Ω$ is 0.3 A, while the ammeter reads 0.9 A. The value of $R_{1}$ is ________ $Ω$ . [2024]