Deck 4: Watt/Meters and Energy Meters

Question 1

In an electro dynamometer type of wattmeter

A)the current coil is made fixed
B)the pressure coil is fixed
C)any of the two coils current coil or pressure coil can be made fixed.
D)both the coils should be movable.

Answer 1

the current coil is made fixed

Question 2

In electro dynamometer type of wattmeter current coils designed for carrying heavy currents use stranded wires or laminated conductors :

A)to reduce iron losses
B)to reduce hysteresis losses
C)to reduce eddy current losses in the conductors
D)all of the above.

Answer 2

to reduce eddy current losses in the conductors

Question 3

In an electro dynamometer type of wattmeter , the inductance of the pressure coil circuit produces error :

A)which is constant irrespective of the power factor of the load
B)which is higher at low power factors
C)which is lower at low power factors
D)none of the above.

Answer 3

which is higher at low power factors

Question 4

The power in 3ph 4 wire circuit can be measured by using:

A)five watt meters
B)four watt meters
C)three watt meters
D)1 watt meter.

Question 5

The resistance in the circuit of the moving coil of a dynamometer wattmeter should be

A)almost zero
B)low
C)high
D)none of the above

Question 6

A dynamometer wattmeter can be used for

A)both d.c. and a.c.
B)d.c. only
C)a.c. only
D)any of the above

Question 7

The pressure coil of a wattmeter should be connected on the supply side of the current coil when

A)load impedance is high
B)load impedance is low
C)supply voltage is low
D)none of the above

Question 8

In a low power factor wattmeter the pressure coil is connected

A)to the supply side of the current coil
B)to the load side of the current coil
C)in any of the two meters at connection
D)none of the above

Question 9

In a low power factor wattmeter the compensating coil is connected

A)in series with current coil
B)in parallel with current coil
C)in series with pressure coil
D)in parallel with pressure coil

Question 10

In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at

A)0°
B)60°
C)90°
D)120°

Question 11

The power factor of a single phase load can be calculated if the instruments available are

A)one voltmeter and one ammeter
B)one voltmeter, one ammetqr and one wattmeter
C)one voltmeter, one ammeter and one energy meter
D)any of the above

Question 12

The power of a n-phase circuit can be measured by using a minimum of

A)(n - 1) wattmeter elements
B)n wattmeter elements
C)(n + 1) wattmeter elements
D)2n wattmeter elements

Question 13

A Dynamometer type wattmeter responds to the:

A)average value of the active power
B)average value of the reactive power
C)peak value of the active power
D)peak value of the reactive power

Question 14

The power measurement in a balanced 3-phase circuit can be done by:

A)one wattmeter method
B)two wattmeter method
C)three wattmeter method
D)any of the above method

Question 15

The braking torque provided by a permanent magnet in a single phase energy meter is proportional to the

A)square of the flux of the permanent magnet
B)speed of the meter
C)distance of the permanent magnet from the centre of the revolving disc
D)all of the above.

Question 16

Which of the following is integrating instruments?

A)power factor meter
B)energy meter
C)voltmeter
D)ammeter

Question 17

The phenomenon of creeping occurs in

A)voltmeter
B)ammeter
C)wattmeter
D)watt-hour meter

Question 18

Hole s are drilled on the opposite sides of the spindle of an energy meter to avoid

A)balance of the disc
B)dissipate heat generated due to eddy currents
C)avoid creep on load
D)increase the deflection torque

Question 19

The pressure coil of an induction type energy meter is

A)highly inductive
B)highly resistive
C)purely inductive
D)purely resistive

Question 20

Which type of damping is used in Induction type energy meter?

A)air friction
B)fluid friction
C)gravity
D)eddycurrent

Question 21

In an Induction type energy meter, maximum torque is obtained when the parameter of the rotating disc are

A)r=0
B)x=0
C)r=x
D)none of the above

Question 22

An Induction meter meter can handle current upto

A)10a
B)30a
C)200a
D)100a

Question 23

In an induction type energy meter, compensation for static friction is provided by

A)drilling holes in the disc
B)lag circuits
C)shading bands
D)none of the above

Question 24

Which of the following statements is wrong

A)there is control spring
B)there is a brake magnet
C)creeping error is present
D)disc revolves continuously

Question 25

Which of the following is an essential part of a induction type of meter ?

A)an operating torque system
B)a braking device
C)revolution registering device
D)all of the above