D-1 1phase AC Circuits Flashcards
What is a capacitor?
a device designed to store electrical charge (composed of 2 surfaces/metal plates separated by an insulating material called the dielectric
What unit is capacitance measured in?
farads (F)
What would happen if a capacitor was attached to a power supply?
the electrons would be unable to move and could not bridge the gap due to the insulating material. if the insulator was removed, an electrical discharge would occur
Why are capacitors used to stabilize a fluctuating power supply?
because if the voltage in the circuit drops, the capacitor will release charge to restore the voltage
The magnitude of voltage induced in a turn of wire is proportional to the rate of change of flux passing through that turn.
Faraday’s Law of electromagnetic induction
e=Blv
Fleming’s left hand rule
Thumb - Thrust
First finger - Flux Direction
Middle finger- Movement of electrons
The direction of the induced emf must be such that any current resulting from it will develop a flux that will oppose any changes in the original flux
Lenz’s Law
Mathematically how are inductors treated
just like resistors in series A+B=C in parallel (1/A)+(1/B)=(1/C)
Mathematically how are capacitors treated
the opposite of resistors in series (1/A)+(1/B)=(1/C) in parallel A+B=C
ELI the ICEman?
ELI = Inductor E leads I ICE= Capacitor I leads E
Phase relationship between VXC and IXC in a capacitor?
IXC leads VXC by 90 degrees
Capacitance ( C ) is the property of an electric circuit that opposes a change in ?
Voltage
Basic capacitor consists of two ______ separated by an insulating material called the ______
Metal Plates, Dielectric
Factors that determine the amount of capacitance of a capacitor are?
- area of plates
- distance between plates
- different types of material as dielectric
Inductance ( L ) is the property of a circuit which opposes ?
a change in Current
What is the unit of measurement for Inductance ( L ) ?
Measured in Henry ( H )
What are four factors that affect the Inductance of a coil?
- Number of Turns
- Permeability of core
- area of core
- Length of magnetic path
an Inductor is more effective if the coils are wrapped around a ?
Iron Core
a simple inductor or coil is made up of ?
Turns or Coils of wire
If the number of turns on a coil is increased the Inductance will?
Increase
If the core of a coil is replaced by one with a lower permeability the inductance will ?
decrease
if the length of the magnetic path in the core of a coil is decreased the inductance will ?
Increase
the ability of an insulating material to withstand high voltage without breakdown is know as
Dielectric Strength
Capacitive Reactance (XC) is the opposition to the _____ in a ac circuit containing a capacitor?
Current
Capacitive Reactance (XC) in measured in ?
Ohms
Formula for XC ?
XC = (1) / (2)(pie)(f)(C)
if the cross sectional area of the core is reduced the inductance of a coil will?
decrease
What is Induction?
process by which a voltage is produced by the interaction of a conductor and a magnetic field
what is faradays law?
the amount of induced emf is directly proportional to the rate of change of flux
Mutual Induction is ?
the generation of an emf into one conductor or circuit by a change in flux around a separate conductor or circuit
self induction is?
the generation of an emf in a conductor or circuit by a change of flux in the same circuit
Factors effecting counter emf in a coil
- Inductance of the coil
2. rate of change of current in the coil
Inductive Reactance ( XL ) is the ________ created by inductance in an ac circuit?
Opposition
XL is measured in ?
Ohms
Two factors affecting XL ?
Inductance
Frequency
equation for XL?
XL = 2(pie)(f)(L)
What is the relationship between iXL and VXL in a purely inductive circuit?
iXL lags Vxl by 90 degrees
