1 Flashcards
First discovered 2000 yrs ago by Greeks
Lodestone (magnetism) natural magnet
Magnetic fields must oppose each other in these ways to demagnetize
Be struck hard, heat, reversing magnetic field
The end of the magnet pointing to north and south are?
North Pole and South Pole
What are the attraction and repulsion laws
Like poles repel, unlike poles attract
____ __ _____ in a magnet extend out into space from the N pole to the S pole
Lines of force
Left hand rule:
Thumb towards electron flow, fingers point towards magnetic field direction
If # of loops are wound in same direction to form a coil, ____ _____ will add to make ____ _____ more dense.
More fields; flux lines
A _______ _____ is used which has an extra set of contacts to keep current flowing through the relay even after the main switch is released.
Holding relay
3 sections of transistors
Base, emitter, collector
Whole circuits, manufactured with all components in place and ready to work are______ ______
Integrated circuits
Two kinds of meme pry systems in common use are the ______ ______ ________ and the ____-_____ ______
Random access memory (temporary stored info); read- only memory (prearranged)
Potential energy is most nearly associated with:
Force
The accomplishment of a force acting through a distance is associated with:
Work
Energy available for future use is called:
Potential
The term “power” means:
Rate at which work is done
Falling water contains:
Kinetic energy
The acceleration of a freely falling body due to the force of gravity is :
32 ft/ second
A foot lb is a unit of:
Work
In 5 sec of fall, a falling body will fall a total of:
400 ft (d=1/2gt^2)
The theoretical velocity of a freely falling body is equal to:
Square root of 2GH
If the velocity of a stream of water is doubled the weight of a material it can suspend and carry is increased by:
16 times
A pump raises 200 cubic ft of water to a height of 50 ft. How much was done to raise this water
624,000 ft lbs (200 x 62.4) x 50
If the water in the above question is raised in 5 min. At what rate in horse power is the work done?
3.75
Niagara falls is 160 ft high. At the top of the falls each cubic ft of water (62.4 lbs) has how many ft-lbs of potential energy
9984
Increasing the velocity of falling water will:
Increase available kinetic energy
Disregarding all other losses, rate of flow of a liquid is the product of:
Area x velocity
If the diameter of a pipe is decreased uniformly at its termination and with no change in pressure head, the exit velocity of the liquid is:
Increased
With continuous steady flow, the tota head at any point ina. Stream is equal to the total head at any downstream point plus the:
Loss of head between the two points
The sudden transformation within a pipe of the kinetic energy of the moving mass is water into pressure energy is the most usually associated with:
Water hammer
The damaging effects of water hammer can be controlled by:
Proper valve control, venting and print
All of the ______ _______ May be step up and step down windings, or some may be step up and some step down.
Secondary windings
Primary windings is ____ __ ___ _____ in the secondary times the number of turns in the secondary winding.
Equal to the current
The ____ ______ is a special type of iron core transfer which has one winding which serves as primary and secondary.
Auto transfer
I^R losses are called _____ _____.
Copper losses
____ ______ in a transfer core are reduced by dividing the core into many flat sections, or laminations that’s really insulated from each other
Eddy currents
The capacitance if a capacitor is determined by what three things
Surface area of the plates
The distance between plates
Insulating material (dielectric)
The capacitor voltage is often called a ____ ____ because it acts 180 degrees out of phase with applied voltage
Counter voltage
Capacitive reactance is expressed in…
Ohms
Component vectors in the same direction can be added…
Arithmetically
The closer the current is to being in phase with the applied voltage, the more what?
Resistance
Inductance ____ current
Leads
A vector has _____ and ____
Magnitude; direction
In and inductive circuit applied voltage ____ current by 90 degrees
Leads
In a capacitive circuit the current ____ applied voltage by 90 degrees
Leads
Multiplying apparent power by the cosine of the phase angle between voltage and current
True power
Like current in a parallel RL circuit is equal to the ____ ___ of the currents in the resistive and inductive branches.
Vector sum
A ________ Shows the magnitude and direction of the current or voltage at every incident of time
Waveform
The effective value is also called the ____ ____ ______ or rms value
Route mean square
The ____ Consumed in any circuit depends on the voltage and current in the circuit
Power
The two reasons for an increase in resistance are
When an ac current flows in a conductor
It causes voltages to be set up inside of the conductor
The magnitude of the ____ at any instant is directly proportional to the magnitude of the _____ at that instant and is inversely proportional to the value of resistance
Current; voltage
The magnitude of the induced emf is directly proportional to the _____ of the magnetic Field, the link of the conductor, and the speed at which the conductor moves through the magnetic field
Strength
The relationship between the induced EMF and the applied voltage that causes the current flow is such that the two voltages are always
180 degrees out of phase
Since the action of the induced emf is to oppose the applied voltage it is often called the ____ or ______ ___
Back; counter emf (cemf)
One factor that effects self induction is the ______ _____ of the conductor
Physical shape
Unit of inductance is
Henry
If an AC circuit has only resistance the voltage and current in the circuit are
In phase
What are the four functions of the gear system
Transmit positive force
change direction
change speed
increase and decrease Force
Electromagnetic circuit breaker uses the principle of ____ to open a circuit When too much current flows
Magnetism
When a compound is broken down into a small form
Molecule
A material substance made of like chemicals that unite chemically
Element
Material substance made of unlike chemicals that unite chemically
Compound
Which of the four elements listed is the lightest per unit of volume
Calcium
Which of the four elements listed is the lightest per atomic weight
Carbon
Water is a
Compound
When two or more atoms combine chemically the particle this formed is a
Molecule
A compound is formed when the atoms of two or more elements become
Chemically bonded
Our air (atmosphere) is composed by volume of
21% oxygen and 79% nitrogen
Atmospheric pressure at sea level is normally considered to be approximately
14.7 psi
When molecules are tightly bound they are in a
Solid state
Liquids offer a high resistance to any force tending to change their
Volume
A pound is a unit of
Force
A temp reading of 59 degrees F is equal to
C= 5/9(F-32) F= 9/5 C+32
15 degrees C
A temp reading of 85 degrees C is equal to
C= 5/9(F-32) F= 9/5 C+32
185 degrees F
Density is a ratio between mass and?
Volume
When the temp of a substance increases or the pressure is reduced the substance does what
Expands and becomes less dense
If an objects weight is 210 lbs and volume is 3.5 cu ft what is the density
60 ft^3
Water has a density of 62.4 lbs/ft^3. the volume of 1000 lbs of water is
16ft^3
What can be used to find the weight of objects which cannot be weighed on scales
Specific gravity
A piece of concrete weighs 400 lbs in air and 350lbs in water what is the specific gravity
Weight in air/ weight in air -weight in water
8
Specific weight most nearly means
Density
Atmospheric pressure is _____ at sea level
Greater
The term viscosity most nearly means?
Resistance to physical change
What is the pressure on the bottom of a discharge line at 200ft?
12,480lbs/ft^2
The pressure upward at any given point in a liquid is ____ the downward pressure at that point
The same as
A slanting penstock 2000ft king conveys water from a reservoir to a turbine 800ft below the level of the reservoir the pressure at the turbine would be?
800x62.4
49,920lbs/ft^2
What is the force on the bottom of a tank 6ftx8ftx12ft filled to a depth of 3ft with water
8985.6lbs
How to get Gauge pressure to absolute pressure @sea level conditions
Add 14.7
The pressure against a large piston in a confined space is
Proportional to the area on a small piston
Fluid pressure might be expressed properly by?
Lbs/in^2
The forces that are req’d to move fluid through a siphon are:
Friction head and static head
If you need to measure with accuracy greater than hundredth of in. You use a?
Vermiar caliper
