Extension of Ammeter and Voltmeter

Q. A moving coil instrument having a resistance of $10\Omega$, gives a full-scale deflection when the current is 10 mA. What should be the value of the series resistance, so that it can be used as a voltmeter for measuring potential difference up to 100 V?

1. $9990\Omega$
2. $990\Omega$
3. $9\Omega$
4. $99\Omega$

Q. A moving coil instrument whose resistance is $25\Omega$ given a full-scale deflection with a voltage of 25 mV. The instrument is to be used with a series multiplier to extend its range to 10 V. Then the error caused by ${10}^{\circ }C$ rise in temperature is (The temperature coefficient of copper is $0.004\Omega /{\Omega }^{\circ }C$ and that of margin $0.00015\Omega /{\Omega }^{\circ }C$)

1. 0.16% low
2. 0.16% fast
3. 0.24% low
4. 0.24% fast

Q. A DC voltmeter has a sensitivity of $1000\Omega /volt.$ When it measures half of full scale in 100 V range, the current though the voltmeter is

1. $100mA$
2. $1mA$
3. $0.5mA$
4. $50mA$

Q.

An emf of$20V$ is applied at time$t=0$ to a circuit containing in series $10mH$ inductor and $5\Omega$ resistor. The ratio of the currents at time $t=\infty$ and$t=40s$ is close to take $e^2=7.389$.

1. $1.06$

2. $1.46$

3. $1.15$

4. $0.84$

Q. A full scale deflection current of a meter is 2 mA and its internal resistance is $500\Omega$. The instrument is required to be used as voltmeter with full scale deflection of 200 V. The value of series resistor required should be

1. $90.4k\Omega$
2. $99.5k\Omega$
3. $99.9k\Omega$
4. $90.4k\Omega$

Q. A DC ammeter has a resistance of $0.1\Omega$ and its current range is $0-100A$. If the range is to be extended to $0-500A$, then meter requires the following shunt resistance

1. $0.010\Omega$
2. $0.011\Omega$
3. $0.025\Omega$
4. $1.0\Omega$

Q. An ammeter has a current range of 0-5 A, and its internal resistance is $0.2\Omega$. In order to change the range to $0-25A$ , we need to add a resistance of

1. $0.8\Omega$ in series with the meter
2. $1.0\Omega$ in series with the meter
3. $0.04\Omega$ in parallel with the meter
4. $0.05\Omega$ in parallel with the meter

Q. A $100\mu A$ ammeter has an internal resistance of $100\Omega$. For extending its range to measure $500\mu A$, the shunt resistance required is of

1. 20.0 $\Omega$
2. 22.22 $\Omega$
3. 25.0 $\Omega$
4. 50.0 $\Omega$

Q. A galvanometer with a full scale current of 10 mA has a resistance of $1000\Omega$. The multiplying power (the ratio of measured current to galvanometer current) of $100\Omega$ shunt with this galvanometer is

1. 110
2. 100
3. 11
4. 10

Q. The value of series resistance to be used to extend ( 0- 200) V range voltmeter having $2000\Omega /V$ sensitivity to be extended to ( 0-2000) V range.

1. $3600k\Omega$
2. $5500k\Omega$
3. $3400k\Omega$
4. $4500k\Omega$

Q. A(0-50 A) moving coil ammeter has a voltage drop of 0.1 V across its terminals at full scale deflection. Then external shunt resistance (in milliohms) needed to extend its range to (0-500 A)is

1. 0.22

Q. Three moving iron type voltmeters are connected as shown below. Voltmeter readings are $V,V_1$ and $V_2$ as indicated . The correct relation among the voltmeter readings is

1. $V=\frac{V_1}{\sqrt{2}}+\frac{V_2}{\sqrt{2}}$
2. $V=V_1+V_2$
3. $V=V_1{V}_2$
4. $V=V_2-V_1$

Q. A 1000 V DC supply has two 1-core cables as its positive and negative leads: their insulation resistances to earth are $4M\Omega$ and$6M\Omega$, respectively, as shown in the figure. A voltmeter with resistance $50k\Omega$ is used to measure the insulation of the cable. When connected between the positive core and earth, then voltmeter reads

1. 8 V
2. 16 V
3. 24 V
4. 40 V

Q. When the voltage across a battery is measured using a dc potentiometer, the reading shows 1.08 V. But when the same voltage is measured using a Permanent Magnet Moving Coil (PMMC) voltmeter, the voltmeter reading shows 0.99 V. If the resistance of the voltmeter is $1100\Omega ,$ the internal resistance of the battery, in $\Omega$ is

1. 100

Q. For a given frequency, the deflecting torque in an induction type ammeter is directly proportional to

1. $curren{t}^2$
2. $curren{t}^3$
3. $\sqrt{current}$
4. $current$

Q. Two ammeters X and Y have resistances of $1.2\Omega$ and $1.5\Omega$ respectively and they give full scale deflection with 150 mA and 250 mA respectively. The ranges have been extended by connecting shunt so as to give full scale deflection with 15 A.
The ammeters along with shunts are connected in parallel and then placed in a circuit in which the total current flowing is 15 A. The current in amperes indicated in ammeter X is

1. 10.28

Q. A 2 A full-scale PMMC type dc ammeter has a voltage drop of 100 mV at 2 A. The meter can be converted into a 10 A full-scale dc ammeter by connecting a

1. $12.5m\Omega$ resistor in parallel with the meter
2. $12.5m\Omega$ resistor in series with the meter
3. $50.0m\Omega$ resistor in parallel with the meter
4. $50.0m\Omega$ resistor in series with the meter

Q. A galvanometer with internal resistance $100\Omega$ and full-scale current 1 mA is used to realize a dc voltmeter with a full scale range of 1 V. The full scale range of this voltmeter can be extended to 10 V by connecting an external resistance of value

1. $9k\Omega$
2. $9.9k\Omega$
3. $10k\Omega$
4. $11k\Omega$