craft
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Author:
Hazard
ID:
291786
Filename:
craft
Updated:
2014-12-16 17:27:53
Tags:
craft
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Description:
craft
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The resistance to magnetic flux is called
reluctance
What is the MKS unit for magnetic flux
Weber
Hardened steel is difficult to magnetize because
of its low permiability
to measure electrical potential you should use a
Voltmeter
How should a voltmeter be connected in a circuit to measure voltage?
In parallel with the potential points being measured
What is used to measure electrical resistance
ohmmeter and meg-ohmmeter
What property of a material is present in every electrical circuit?
resistance
Resistors are connected to electrical circuits to
Limit current
Resistors connected in series across a voltage source to obtain a lower voltage are called voltage
dividers
opposition to any voltage change in a circuit is caused by
capacitance
What is the basic unit for measuring the capacitance of a capacitor
Farad
When capacitors are connected in parallel the effective capacitance of the circuit is
increased
the opposition to any crrent change in an ac circuit caused by inductance is called
inductive resistance
Unit used to measure inductive resistance
Ohm
The ineraction between the roto and stator in an ac motor that causes the rotor to rotate is caused by the
magneticfeilds
In a Y connected load or source, the line voltage is found by what formual?
El= sqroute 3Ip
the formula for finding line current in a Y connected load or source is
IL=Ip
In a delta connected load what formula
EL=EP
The Cos 0 used in 3 phase power formulas is the
power factor
One way of measuring power in a 3 phase circuit is by the use of
3-wattmeters
When measuring the power of a 3 phase circuit at 50 percent power factor using only two watt-meters one watt-meter will read
Zero
Dielectric strength is usually expressed in
volts
few electrons and poor conductor is
insulator
what are insulating materials sometimes called
Dielectrics
by how much dose the heat caused by current flowing through a wire increase?
the square of the increase in current
Ohms law simple terms
The higher the voltage the more current flow through a given resistance
Desirable characteristics of conductor insulation include
flexibility and mechanical strength
A channel that holds and protects cables or wires is a
Raceway
BX cable has the same general characteristics as
flexible conduit
to which transformer winding is voltage supplied?'
Primary
To which transformer winding is the load connected?
Secondary
The volt amperes of the primary winding and the volt amperes of the secondary winding are
equal
The output or capacity of a transformer is measured in
kVa
Transformer losses are classified as copper losses and
core losses
Transformer core eddy current losses are reduced by using a
laminated core
What voltage will appear across the secondary terminals of an auto transformer if the common winding should open
primary
A variable transformer is a continuously adjustable
autotransformer
while working on a current transformer the secondary winding must be
short circuited
electric current is measured in amperes which are
Coulomb per second
According to ohms law voltage is equal to
resistance times current
What happens to total current flow if the voltage of a series circuit is doubled and the resistance stays constant
doubles
What is common to all components of a series circuit
current
if one leg of parallel circuit develops an open the total current will
decrease
What is common to all components of a parallel circuit
voltage
General purpose transformers are usually
dry type
A synthetic liquid used in Transformers is known as
askarel
With a delta delta transformer if one transformer is damaged and removed from service the two remaining transformers can be connected as
open Delta
In what type of 3 phase motor starters are auto transformers used
compensating
The installation of dry type transformers in doors are covered by what rules
NEC