4. Transformers Flashcards
changes the intensity of alternating voltage and current by mutual induction
Transformer
is used to change the magnitude of voltage and current in an AC circuit
transformer
a transformer with a turns ratio greater than 1 is a _____ transformer
step up
a transformer with a turns ratio lesser than 1 is a ____transformer
step down
increasing the turns, ______ the voltage but ______ the current
increases (v),
decreases (c)
Voltage and turns are _____ proportional
directly
Current and turns are _____ proportional
inversely
Power =
Power = Voltage x Current
THE THREE MAIN CAUSES OF TRANSFORMER INEFFICIENCY
- Resistance
- Hysteresis
- Eddy currents
electric current in the copper wire experiences resistance that results in heat generation
Resistance (Copper Losses)
the alternate reversal of the magnetic field caused by the alternating current causes and additional resistance (electricity induces magnetism)
Hysteresis
these current oppose the magnetic field that induced them, creating a loss of transformer efficiency (magnetic field induces electricity)
Eddy Currents
TYPES OF TRANSFORMER
- Closed-core transformer
- Autotransformer
- Shell-type transformer
built about a square core of ferromagnetic material
Closed-core transformer
consists of an iron core with only one winding of wire about it
Autotransformer
based on self-induction rather than mutual induction
Autotransformer
confines even more of the magnet field lines of the primary winding because the secondary is wrapped around it and there are essentially two close core
Shell-type transformer
is a device that stores electrical energy in an electric field
Capacitor
the relationship between the charge put on the body and its potential
Electrical Capacitance
charge divided by potential
Capacitance (C = Q divide by V)
SI unit of capacitance
Farad
farads=
farads= coulombs/volts
is to consider capacitance in terms of change of charge divided by the corresponding change in potential
Alternative definition of capacitance
is the process of converting alternating voltage to direct voltage and therefor alternating current to direct current
Rectification
inhibits flow of electrons
Resistor
provides electric potential
Battery
momentarily stores electric charge
Capacitor
measures electric current
Ammeter
measures electric potential
Voltmeter
turns circuit on or off by providing infinite resistance
Switch
increases or decreases voltage by fixed amount (AC only)
Transformer
variable resistor
Rheostat
allows electrons to flow in only one direction
Diode
