PHEP 25

Question 1

A DC METER MAY BE COMPARED TO AN ELECTRIC

Answer 1

MOTOR

Question 2

IN A D’ARSONVAL TYPE METER THE PRIMARY PURPOSE OF THE IRON CORE IS TO

Answer 2

CONCENTRATE THE FLUX BETWEEN THE CORE AND THE POLE PIECE

Question 3

THE D’ARSONVAL MOVEMENT OPERATES ON THE PRINCIPLE OF

Answer 3

MAGNETIC REPULSION AND ATTRACTION

Question 4

IN MOST D’ARSONVAL MOVEMENTS DAMPING IS ACCOMPLISHED AUTOMATICALLY WITHOUT THE NECESSITY FOR ATTACHING SOME FORM OF AIR VANE AND CONTAINER TO THE MECHANISM. THIS STATEMENT IS:

Answer 4

TRUE BECAUSE OSCILLATION OF THE MOVEABLE COIL OR BOBBIN CREATES INDUCED CURRENTS IN THIS COIL WHICH OPPOSES THE MOTION OF THE COIL

Question 5

A ZERO ADJUSTMENT SCREW IS PROVIDED ON MOST DC METERS IN ORDER TO ADJUST THE

Answer 5

POINTER TO THE ZERO SETTING SHOULD IT BE OFF THAT POINT

Question 6

THE GRADUATIONS OF THE CALIBRATED SCALE ON A D’ARSONVAL METER ARE UNIFORM. THIS IS BECAUSE THE DEGREE OF ARMATURE ROTATION IS

Answer 6

DIRECTLY PROPORTIONAL TO THE CURRENT

Question 7

IN A DC WATTMETER THE 2 CURRENT COILS AND SINGLE VOLTAGE COIL ARE SO CONNECTED THAT

Answer 7

THE VOLTAGE COIL IS IN PARALLEL TO THE LINE AND THE CURRENT COILS ARE IN SERIES WITH EACH OTHER AND THE LINE

Question 8

BEFORE USING AN OHMMETER THE LEADS SHOULD BE SHORTED TOGETHER AND THE VARIABLE RESISTANCE KNOB ADJUSTED SO THAT THE METER READS

Answer 8

0 OHMS

Question 9

A SHUNT IS CONNECTED IN PARALLEL WITH THE COIL OF A DC AMMETER TO PERMIT THE METER TO MEASURE LARGER AMOUNTS OF CURRENT THAN THE METER COIL COULD SAFELY CARRY. THIS STATEMENT IS:

Answer 9

TRUE BECAUSE THE CURRENT BEING MEASURED IS CAUSED TO DIVIDE ITSELF BETWEEN THE COIL AND THE RESISTOR

Question 10

WHEN HAIRSPRINGS ARE USED IN A D’ASONVAL TYPE METER THEY

Answer 10

SERVE AS CONDUCTORS,
WOUND OPPOSITELY AND PROVIDE RESTORING FORCES,
ATTACHED TO THE ENDS OF THE BOBBIN

Question 11

CURRENT-MEASURING INSTRUMENTS MUST ALWAYS BE CONNECTED IN

Answer 11

SERIES WITH THE CIRCUIT

Question 12

WHAT 2 CONDITIONS MAY BE OBSERVED IN A BRIDGE CIRCUIT

Answer 12

BALANCE AND UNBALANCE

Question 13

IN FIRST USING A MULTI-RANGE DC VOLTMETER ON A CIRCUIT OF UNKOWN VOLTAGE SET THE RANGE SELECTOR AT

Answer 13

THE HIGHEST POINT AND WORK DOWNWARD INTIL THE PROPER RANGE IS DETERMINED

Question 14

WITH AN OHMMETER SETTING ON THE RX1 SCALE IT TAKES 0.01 MILLIAMPERES TO DEFLECT THE POINTER TO HALF SCALE. IF THE METER WAS SET ON THE RX100 SCALE HOW MUCH CURRENT WOULD IT TAKE TO DEFLECT THE POINTER TO HALF SCALE

Answer 14

0.01 MILLIAMPERES

Question 15

THE RATINGS OF 4 VOLTMETER ARE SHOWN BELOW. WHICH ONE WOULD HAVE THE GREATEST SENSITIVITY?

Answer 15

100,000 OHMS PER VOLT

Question 16

THE MAXIMUM CURRENT NORMALLY CARRIED IN A PARTICULAR CIRCUIT IS 150 AMPERES. THE DC AMMETER BEST ADAPTED TO THIS CIRCUIT FROM THE STANDPOINT OF SAFE AND EFFICIENT OPERATION SHOULD HAVE A RANGE OF

Answer 16

O-300 AMPS

Question 17

THE LEAST AMOUNT OF METER ERROR COULD BE EXPECTED FROM A OHMMETER READING OBTAINED

Answer 17

FROM THE MAXIMUM DEFLECTION AREA OF THE POINTER

Question 18

A METER IS SAID TO HAVE GOOD DEFECTING TORQUE CHARACTERISTICS WHEN

Answer 18

THE METER RESPONDS PROMPTLY TO CHANGES IN THE MEASURED FORCE

Question 19

WHEN USING A DCC VOLTMETER

Answer 19

ALWAYS CONNECT THE METER IN PARALLEL ACROSS THAT PORTION OF THE CIRCUIT FOR WHICH A VOLTAGE VALUE IS DESIRED, IT IS BEST TO START WITH A RANGE LARGE ENOUGH TO INSURE LESS THAN FULL SCALE DEFLECTION, IT IS NECESSARY TO OBSERVE THE PROPER POLARITY

Question 20

IN THE WHEATSTONE BRIDGE TYPE CIRCUIT ON THE NEXT PAGE THE BRIDGE CURRENT IS TOWARD POINT “A”. THE RESISTANCE OF RX IS

Answer 20

45 OHMS