Download Answer the following questions :-

Chapter - 2
Questions
Answer the following questions :Show True or False :1- When connecting shunt resistance Rsh to the meter movement this will increase
the range of the current measurement .
(
)
2- When connecting shunt resistance Rsh to the meter movement the sensitivity will
decrease.
(
)
3- The clamp-on meter is used only to measure AC current .
(
)
4- The average power in an AC circuit is measured by wattmeter
(
)
5 - To get accuracy of voltage and current measurements select the scale that cause
deflection of pointer at mid scale.
(
)
6 - The clamp-on meter is used only to measure DC current without opening the
circuit.
(
)
7 - In Wattmeter:
a- In wattmeter, current through moving coil is proportional to the voltage across the
load and is in phase.
(
)
b- Deflecting torque is directly proportional to current and to the strength of the
magnetic field.
(
)
c- Average value for AC power = Constant value for DC power.
(
)
d- Power Factor sin Φ = Watts / Volt x Ampere
(
)
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Switching Section
Chapter - 2
Questions
Complete the following :The clamp-on meter is used only to measure ……………………………………
1.
2- The average power in an AC circuit is measured by …………………………….
3- To solve the problem of drawback when changing positions of the range in an
elementary multi-range ammeter, we can :
i- ……………………………………………………………………………………
ii- …………………………………………………………………………………..
iii- …………………………………………………………………………………..
4- The Ammeter is to be protected from high currents, during time of change range
because it may cause for the ammeter the following defects :
a- ………………………………………………
b- ………………………………………………
c- ………………………………………………
5- Why a make-before-break switch is used to select the ammeter shunts?
………………………………………………
………………………………………………
6 - In Wattmeter:
a- The wattmeter uses an ………………………. Movement .
b- In measuring power, the wattmeter is connected,so that the load current flow
through the…………………… coil.
c- In wattmeter, the moving coil is connected ………… the line ……………… with the
load.
d- In wattmeter, a ……………………… is connected in …………….. with the moving
coil.
e- In wattmeter, in any given position of the coil ,the deflecting torque is
………………….. to the power e x I
f- Wattmeter is used to measure …………….. and …………………. Power.
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Switching Section
Chapter - 2
Questions
Solve the following :
1 ) Assuming that a 50 μA, 2 K Ω movement is available ,
Design an ammeter that provides the following ranges :
0 –1 ma
0 – 5 ma
0 – 100 ma .
( Calculate the shunt resistance for each range).
Range
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Rm
Switching Section
Chapter - 2
Questions
2 – A meter movement 50 μA, 2 K Ω coil resistance is usd to construct aytron shunt
ammeter. The resistance values are R1=1 Ω , R2 = 10 Ω ,and R3 = 95 Ω
A ) Draw the circuit for ranges 1 ma, 10 ma, 100 ma .
B ) Calculate :
1- The effective shunt resistance for each range ( RSHE ).
2- The effective meter resistance. ( RME ).
3- The input resistance ( RIN ).
4- Accuracy of the meter on the scales, if the RTH for the circuit
under measurements is 40 K Ω. ( RTH = 40 K Ω )
5- Error for each range.
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Switching Section
Chapter - 2
Questions
Questions :
1 ) a - Supply the main parts on the figure of clamp-on meter and then complete the
questions ? :
1 ) The purpose of the moving coil is to ........................................................
.......................................................................................................................................
.......................................................................................................................................
2 ) The purpose of the spring is to ......................................................................
.......................................................................................................................................
.......................................................................................................................................
3 ) The purpose of the rectifiers is to ...............................................................
.......................................................................................................................................
.......................................................................................................................................
4 ) The clamp-on meter is used to measure ………………….. with ………….values
without ……………… the circuit .
5 ) The clamp on meter consists of :
a) ………………………………………………….
b) ………………………………………………….
c) …………………………………………………..
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Switching Section
Chapter - 2
Questions
Choose the correct answer :1 ) When measuring current Im = 15 μA it is better to use
a ) IFS = 50 μA scale.
b ) IFS = 30 μA scale.
c ) IFS = 35 μA scale.
d ) IFS = 20 μA scale.
2 ) The clamp-on meter is used to measure :
a ) Power.
b ) D.C. current.
c ) A.C. voltage
d ) High values A.C. current without opening the circuit.
3 ) To build an ammeter that measures currents greater than the meter movement
full-scale value, you use a :
a ) 0.001 Ω resistor .
b ) Multiplier resistor .
c ) Shunt resistor.
d ) Voltage divider.
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Switching Section