11. In shunt the potential terminals have a ______
High current capacity
Low voltage capacity
Low current capacity
High voltage capacity
Answer.2. Low voltage capacity
Explanation:
The shunt is a resistance to be used in parallel with the coil of the basic meter movement. The purpose of the shunt is to enable the meter to measure large currents.
Its principal disadvantages are power consumption and the fact that the metering current must be operated at the same potential to earth as the current-carrying line and therefore limits its use to low voltage applications.
12. The meter element of a permanent-magnet moving coil instrument has a resistance of 5 Ω and requires 250 mA for full-scale deflection. Calculate the resistance to be connected to enable the instrument to read up to 1 A.
5 Ω resistance in series
5/3 Ω resistance in parallel
5 Ω resistance in parallel
5/3 Ω resistance in series
Answer.2. 5/3 Ω resistance in parallel
Explanation:
For range extenstion
Rse = Rm(M – 1)
Rm = Vm/Im
Rsh = Rm/(M – 1)
M = Multiplying factor = (Required full scale deflection) / (Initial full scale deflection)
Where,
Rsh = Shunt resistance
Rse = Series resistance
Rm = Meter resistance
Vm = Potential difference across the meter
Im = Meter current
Given –
Rm = 5 Ω
M = 1/(250 × 10−3) = 4
Rsh = 5/(4 − 1) = 5/3 Ω
13. In shunt the current terminals have a ______
High current capacity
Low voltage capacity
Low current capacity
High voltage capacity
Answer.1. High current capacity
Explanation:
A current shunt is in general a four-terminal resistance the current to be measured being connected to the current terminals. The potential terminals are arranged so that an accurately known resistance and voltage drop exists between them, and situated so that they are unaffected by any heating which may occur at the current terminals.
Two terminals with large current carrying capacity are called current terminals. These are used for inserting the ammeter in series with the main circuit. The other two terminals are of small size and are called potential terminals. These are used for connecting the basic meter.
14. A 10A DC Ammeter has a resistance of 0.1 Ω is to be extended to 50 A, the required shunt wire is
Manganin wire of 20 m Ω
Constantan wire of 20 m Ω
Manganin wire of 25 m Ω
Constantan wire of 25 m Ω
Answer.2. Manganin wire of 25 m Ω
Explanation:
A shunt is a low-value resistance having minimum temperature co-efficient and is made up of manganin. Because manganin has a very low value of temperature coefficient.
In the figure
I is total current flowing in the circuit
Ish is the current through the shunt resistor
Rm is the ammeter resistance
For range extension
Rse = Rm(M – 1)
Rm = Vm/Im
Rsh = Rm/(M – 1)
M = Multiplying factor = (Required full scale deflection) / (Initial full scale deflection)
Where,
Rsh = Shunt resistance
Rse = Series resistance
Rm = Meter resistance
Vm = Potential difference across the meter
Im = Meter current
Given –
Rm = 0.1 Ω
M = 50/10 = 5
Rsh = 0.1/(5 − 1) = 0.205 Ω
Rsh = 0.025 Ω = 25 m Ω
Therefore the shunt is made up of 25 mΩ and manganin
15. The shunt resistance is made up of _______
Copper
Manganin
Constantan
Nickel
Answer.2. Manganin
Explanation:
Shunts are used for the range extension of ammeters.
A shunt is a low-value resistance having minimum temperature co-efficient and is made up of manganin. Because manganin has a very low value of temperature coefficient.
16. Extension of moving iron ammeter range can be done by using
Inductor
Shunt
Multiplier
Capacitor
Answer.2. Shunt
Explanation:
Shunts are used for the range extension of ammeters.
A shunt is a low-value resistance having minimum temperature co-efficient.
It is connected in parallel with the ammeter whose range is to be extended. The combination is connected in series with the circuit whose current is to be measured.
The shunt provides a path for extra current as it is connected across (in parallel with) the instrument.
These shunted instruments can be used to measure currents many times greater than their normal full-scale deflection currents.
17. In case of AC ammeters, shunts consist of _______
Impedance
Capacitance
Resistance
Inductance
Answer.4. Inductance
Explanation:
An ammeter shunt creates a very low-resistance connection between two points in an electric circuit. Usually, this shunt creates a voltage drop which allows an ammeter to be used to measure the amperage of a circuit.
If a shunt is to be used with an ammeter operating on a.c., then the inductances of both the ammeter coil and the shunt come into the picture. For the multiplying power to be independent of frequency, the time constants of the ammeter and shunt circuit must be the same.
18. How to convert a (0 to 1) mA meter to measure the current in the range of 1 to 100 mA? The internal resistance of the meter is 100 Ω.
Connect a 1.01 Ω resistance in series with the meter
Connect a 1.01 Ω resistance in parallel with the meter
Connect a 10.01 Ω resistance in series with the meter
Connect a 10.01 Ω resistance in parallel with the meter
Answer.2. Connect a 1.01 Ω resistance in parallel with the meter
Explanation:
For range extenstion
Rse = Rm(M – 1)
Rm = Vm/Im
Rsh = Rm/(M – 1)
M = Multiplying factor = (Required full scale deflection) / (Initial full scale deflection)
Where,
Rsh = Shunt resistance
Rse = Series resistance
Rm = Meter resistance
Vm = Potential difference across the meter
Im = Meter current
Given –
Rm = 100 Ω
M = 100/1 = 100
Rsh = 100/(100 − 1) = 1.01Ω
Rsh = 1.01 Ω
For range extension of current measurement in moving coil instrument, a resistance is connected in parallel or shunt with coil resistance.
19. For voltmeter multiplier the resistance connected in series should be ______
Inductive
Capacitive
Non-inductive
Non-capacitive
Answer.3. Non-inductive
Explanation:
In Voltmeter multipliers, A non-inductive resistance in series with a voltmeter is used to extend the range of the voltmeter. Non-inductive resistors do not store any energy. This has the benefit to avoid generating transients in sensitive circuits such as the galvanometer movements.
It must have a very small temperature coefficient. Manganin resistance is generally used for this purpose. As the amount of power absorbed by it is appreciable, sufficient provision for cooling must be provided.
20. A 2-milliampere meter movement with a coil resistance of 1000 ohms. When 2 milliamperes are flowing through the meter coil and are causing FSD, what will be the voltage developed across the coil resistance?
2 V
0.5 V
1 V
1.5 V
Answer.1. 2 V
Explanation:
Given that,
Internal resistance (Rm) = 1000 Ω
Full scale deflection (IFS = 2 mA
Voltage full scale deflection (VFS = IFSD × Rm = 2000 mV = 2 V
