4th six mnths Flashcards
A DC meter may be compared to an electric:
Motor
In a D’Arsonval type meter, the primary purpose of the iron core is to:
Concentrate the flux between the core and the pole piece
The D’Arsonval movement operates on the principle of:
Magnetic repulsion and attraction
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:
True because oscillation of the moveable coil (or bobbin) creates induced currents in this coil which opposes the motion of the coil.
A zero adjustment screw is provided on most DC meters in order to adjust the:
Pointer to the zero setting should it be off that point
The graduations of the calibrated scale on a D’Arsonval meter are uniform. This is because the degree of armature reaction is:
Directly proportional to the current
In a DC wattmeter, the two current coils and single voltage coil are so connected that:
The voltage coil is in parallel to the line, and the current coils are in series with each other and the line.
Before using an ohmmeter, the leads should be shorted together and the variable resistance knob adjusted so that the meter reads:
Zero ohms
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:
True because the current being measured is caused to divide itself between the coil and the resistor.
When hairsprings are used in a D’Arsonval type meter, they:
All of the above
Current measuring instruments must always be connected in:
Series with the circuit
What two conditions may be observed in a bridge circuit?
Balance and unbalanced
In first using a multirange DC voltmeter on a circuit of UNKNOWN voltage, set the range selector at:
The highest point and work downward until the proper range is determined
With an ohmmeter setting on the RX1 scale. it takes .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?
.01 milliamperes
The ratings of four voltmeters are shown below. Which one would have the greatest sensitivity?
100,00 ohms per volts
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:
0-300 amps
The least amount of meter error could be expected from an ohmmeter reading obtained:
From the maximum deflection area of the pointer
A meter is said to have a good deflecting torque characteristics when:
The meter responds promptly to changes in the measured force
When using a DC voltmeter:
All of the above
In the wheatsone bridge type circuit above the bridge circuit is toward point A. The resistance of Rx is :
45 ohms
In the title block displayed, what letter indicates the size of the original drawing?
A
According to the title block displayed, when was the drawing actually drafted?
11-28-90
A length of spindle shaft is specified on a drawing at 1.5 ft. Which of these actual length measurements is acceptable?
1.49ft
What kind of line does the drafting symbol displayed represent?
Centerline
In section drawings, slanted crosshatch lines represent?
Cut surfaces
Which of the six simple machines is a “continuous lever” with equal arms?
Pulley
The thread specification 10-32 NC-1B LH indicates ____ threads per inch and an ___thread.
32; internal
In the specification 10-32 NC-1B, the screw has a ___ ft and a ___ handed thread.
loose; right
According to the specifications displayed, the weld should be made on ___.
The side opposite the arrow
Sheaves are usually fitted with ____ belts.
V-shaped
On a lathe, the compound rest is the base for the ___.
Tool holder
A drawing that shows all the parts separated from one another is called a(n)?
Exploded view
On a lathe, the top and the swivel are the two main parts of a
Compound rest
What kind of drawing compresses all parts into a two-dimensional plane?
Orthographic projection
A drawing may show all the shafts of a gear train in a single plane in order to___.
Avoid confusion
In the diagram displayed, the width of the side shown is___.
15 in.
Which of the symbols displayed shows a cross-section of a supply duct?
Rectangle with X inside
The part in a duct that directs and spreads the air is called a(n);
Diffuser
The parallel development displayed is for a:
- unfolded box
Square box
What kind of development is used for making a sheet metal piece with a constant taper?
Radial line
The symbol displayed represents____
Fire brick
Most industrial plants specify bearings in terms of___. They specify distances in ___.
North; feet
The location of machinery and equip. in a building is shown in a;
Floor plan
Structural drawings of a building that can be used as a flow diagram is called a(n) ___ drawing.
Elevation
Pascal’s law states that the pressure at a hydraulic system point acts ___.
Equally in all directions
If equal pressure acts on both the rod side and the cap side of a piston, which side receives more force?
Cap side (Blank side)
Rapid pressure changes in a hydraulic system can be prevented by a(n)
Accumulator
The drawing displayed is the symbol for a hydraulic:
Reservoir
The symbol displayed represents ___lines.
Crossing
Threading is the usual method used to join ____ pipes.
Iron
Pipe threads are tapered in order to
Produce a tight joint
Flanged joints are used for joining____ pipes that carry fluids under pressure or at high temperatures.
Large-diameter industrial
Galvanic reaction is the result of joining (a)
Two different kinds of metals
A single-line piping drawing uses___ to show fittings and part sizes.
Symbols
In a wiring diagram, the symbol displayed represents a;
Fuse
The ampere is the unit of measurement for electric:
Current
The metal inside the windings of a transformer is called the
Core
A circuit diagram of a building shows the
Loads supplied by each circuit
A plot plan shows the
Distribution of electricity to all plant buildings
In an air conditioning system, the liquid that changes to a gas as it absorbs heat is called the;
Refrigerant
What part of a refrigeration system controls the flow of refrigerant from high pressure to low pressure?
Expansion vlv
In an air conditioning system, a heat exchanger is part of a(n)
Indirect A/C system
Pneumatic controls in an air conditioning system operate on
Low pressure air
A refrigerant piping drawing is usually a(n) ____ drawing.
Single-line
The main purpose of a sketch is to
Communicate an idea clearly
Objects are shown in 3 dimensions in a(n) ___ sketch.
Pictorial
In a(n) ___ sketch, parts farther from the front are drawn in the same size.
Isometric
In a(n) ___ sketch, parts that are farther away look smaller.
Perspective
Parallel lines…
Never meet
A schematic is made up of:
Symbols and lines
Double line drawings that show the internal details of a pneumatic system are called:
Cutaway drawings
In a DC circuit, the electrons flow from:
One direction only
Arrows are used in a piping diagram to indicate the:
Direction of flow
In a piping system, an alternate flow pattern is indicated by a:
Supplementary diagram
On an electrical diagram, a dashed line indicates a(n):
Exposed wire
Vent lines and drain lines are shown on a hydraulic schematic by
Dashed lines
If a schematic carries no legend, clues about it may be found in the parts list, drawing title, and
Engineer’s notes
The symbol shown below represents a:
*Circle with arrow going through
Gauge
What is the last step in troubleshooting an electrical circuit when using a schematic?
Examine the actual circuit
What electrical symbol represents connecting wires?
*A cross with dot in center
What electrical symbol represents a SPDT sw?
—-o o/ o—
What electrical symbol represents a transformer?
*Two windings with two lines between
What electrical symbol represents a fuse?
*Rectangle with two lines and connecting wires
Which electrical symbol shows NC contacts?
*A Contact with a line crossed through
An electrical circuit in which the current goes from one load to the next is called a ___ circuit.
Series
An electric circuit that allows each load to be turned on or off independently of the others is a ___ circuit.
Parallel
A wiring diagram shows how the parts of a circuit are connected:
Externally
Wires labeled “L” on a schematic:
Carry power from the source.
In the diagram shown below, the “Forward” button is marked:
FOR
The flow of material in a piping system is controlled and adjusted by:
Vlvs
Which symbol below represents a flanged joint?
—-l-l—-
Direction of flow in a piping system may be changed by a(n):
Elbow
What part of a piping system connects different diamters?
Reducer
Which symbol represents a screwed tee fitting?
*A tee with a line drawn on each leg of the tee
A vlv is used to ___ in a piping system.
Control the flow
A cock vlv is used to:
Turn flow on or off quickly
Which symbol below represents a globe vlv?
*A vlv with a colored in dot in the center
A check vlv:
Allows flow in only 1 direction
In the following symbol, the 2-in. dimension is indicated by the letter?
C
Both hydraulic and pneumatic systems:
Are fluid-power systems
In a fluid-power system, a(n) ___ reacts to the pressure of the fluid and does work.
Actuator
The symbol below represents a ___ in a ___ system.
Receiver; pneumatic
The basic symbol for a vlv shows it connections, flow paths, and:
Functions
Which symbol below represents a vlv in the closed position?
*A DCV with 4 ports (no directions)
The composit symbol shown below includes the symbol for a(n):
Electric motor
Which element of a hydraulic braking system directs the flow of brake fluid?
Valve
If the fluid in a hydraulic/ pneumatic system is used again and again it is called a(n) ___ system.
Closed
On a hydraulic/pneumatic diagram, local areas are outlined by which of the following?
Which of the symbols below represents a pushbutton?
*A square with a filled in circle in the middle
In a refrigeration subsystem of an A/C and R system, what is another term for evaporator?
Liquid chiller
What does the following symbol represent?
*A circle with a box on top
Rotary compressor
In an A/C and R system, thermostatic expansion vlvs and ADR vlvs are used in ___ control.
Direct
In a diagram for an electric control circuit, which of the following shows wiring to be installed at the site?
What solid state device in an A/C system can amplify and switch electrical signals?
Transistor
“Fusion” welding means joining two materials by ___ them together
Melting
The basic method of fusion welding that uses the “squeeze-and-heat” process is ___welding.
Resistance
Which of the following is a symbol for a weld with chamfering?
*45 degree angle
If the part is to be welded in the field, the weld symbol includes a(n)
Flag
Standard dimensions for a weld:
May appear in a legend on the welding diagram
Why do we have to measure and control?
So that we may control the quality and quantity of a product
Which of the following is an example of direct measuring?
Gauge glass
What is a mode of control?
All of the above; Proportional, floating, on and off
A device that indicates the value of the controlled variable
Measuring means
Enables the operation to bring about change in the controlled element.
Final control element
Set point:
The desired value of the controlled variable.
The term used to denote the info related to the controlled variable, is sent back to the controlling means so that corrective action can be taken is called feedback?
True
What is lag and what is it caused by?
Time lapse that occurs between the moment a set point change command is sent and when it occurs, caused by primary elements, measuring means, sensors or other items in the system.
The movement the primary element must move before the controlled element starts to move. Where no output action occurs
Dead zone or dead band
The size of a system has no affect on the process reaction rate.
False
Name 4 characteristics that affect performance of controls in an automatic control system.
*R, C, D, C
Response lag
Cycling
Dead band
Capacity
A term derived from the fact the control action produced by the feature is based on the rate at which the controlled variable changes value.
Rate Response
When force is added the vlv will close or pushing up on the vlv stem causes the vlv to close is meant by a reverse-acting vlv.
True
