Amatrol Inductance and Capacitance
How does a buzzer make its sound?
A buzzer is an electromagnetic device that vibrates the armature to produce a buzzing sound.
What is a capacitor?
A capacitor is a device that stores electrical energy in a circuit.
What is a common application of an inductor in an AC cirucit?
A fluorescent light fixture.
How does a motor move?
A motor is an electromagnetic device that produces rotary motion. The motor tranters the motion through a round shaft that rotates inside the magnetic field.
What is a relay?
A relay is an electromagnetic device that is basically an electrically controlled switch.
What is a solenoid and how is the motion produced?
A solenoid is an electromagnetic device that is used most often to produce linear motion. This motion is created by an armature (or plunger) that is inserted inside the coil. When a magnetic field is created, the armature moves.
What happens when the current has stabilized in a DC circuit?
After the current has stabilized, the current though the inductor is determined solely by the DC resistance of the inductor.
What happens after the electromagnetic field's energy is gone in a DC circuit?
After the field's energy is gone, the current remains at the new level until the circuit changes again.
How is an inductor created?
An inductor is created by winding an electrical wire around a coil.
What is a dielectric?
An insulating material that is placed between the conducting plates of a capacitor
Which produces a greater inductive reactance an iron core or an air core?
An iron core
What is capacitance?
Capacitance is the measure of a device's ability to store electrical energy.
What is induced voltage also referred to as?
Counter emf or back emf.
When does current change in a DC circuit?
Current only changes in a DC circuit when the current is first turned on, turned off, or there's a change in load resistance.
_______________________ capacitors must be placed with respect to polarity
Electrolytic
________________________ capacitors provide the most capacitance in the smallest space and at the least cost.
Electrolytic
What are electromagnets?
Electromagnets are devices that use the force created by an electromagnetic field to produce some type of output, usually mechanical motion.
What is the unit of measurement for capacitance?
Farad (F)
The higher the frequency of the AC, the ________________ the inductive reactance.
Greater
The more turns the coil has, the _____________ the inductive reactance.
Greater
What happens in a DC circuit of the resistance of the circuit load increases?
If the resistance of the circuit load increases for some reason, the inductor will react. The electromagnetic field around the inductor collapses, trying to maintain the current at a steady state.
Where is the electrostatic charge stored in a capacitor?
In the capacitor
What is the only time that induced voltage is present?
Induced voltage is only present when the current is changing.
What is inductance a characteristic of?
Inductance is a characteristic of electromagnetic devices that opposes any change in current flow.
What unit is used to measure inductance?
Inductance is measured in the unit Henrys.
When does inductance affect a DC circuit?
Inductance only affects a DC circuit when the current is first turned on, turned off, or when there's a change in the load resistance.
What is inductive reactance?
Inductive reactance applies to AC circuits. It's the inductor's resistance to AC current.
How does inductive reactance and resistance of resistors differ in regard to frequency?
Inductive reactance differs from resistance because the resistance of the resistor is the same at any frequency.
What is another name used to refer to inductors?
Inductors are also referred to as chokes.
What is the total series inductance formula?
LT = L1 + L2 + L3
The invisible force around a wire that is created when current flows through it is called a _______________________.
Magnetic field
What is the name of the invisible force that is created around the wire when electrons flow through a wire?
Magnetic field
What are the five factors that determine the amount of inductive reactance and inductor will introduce into an AC circuit?
Number of turns in the coil diameter of the coil length of the coil type of core frequency of the alternating current
What are the three basic styles of capacitors?
Polarized (AC and DC), non-polarized (mostly DC) and variable
A ________________ is an electromagnetic device that is used most often to produce linear motion.
Solenoid
What are four common electromagnetic devices?
Solenoid Motor Relays Buzzer
What is the stored energy in a capacitor called?
Stored energy is electrostatic charge
The ___________ of the field is proportional to that particular level of current.
Strengh
The ____________ of the field increases as the number of windings (turns) increases.
Strength
What three factors determine the capacitance of a capacitor?
The area of the plates The distance between the plates The type of dielectric used
What is electromagnetism?
The creation of a magnetic field by the flow of electric current is referred to as electromagnetism.
How does the distance of the plates in a capacitor affect the capacitance?
The greater the distance between the plates, the less capacitance.
How does the area of plates affect the capacitance of a capacitor?
The larger the surface area, the greater the capacitance.
How does the opposing effect last in a DC circuit?
The opposing effect lasts only while the current is rising to its steady state value.
What is the purpose of an inductor?
The purpose of an inductor is to resist change is current flow.
What is the reason an inductor resists changes in current flow?
The reason an inductor resists changes in current flow is that whenever current through an inductor is changing, a voltage is induced in the inductor.
What happens when a capacitor stores energy?
The voltage across the leads increases until it has reached the same voltage as the source voltage
What are the parts of a relay?
There are 2 parts of a relay: A coil and one or more sets of switch contacts.
True or false. Since inductors are similar to resistors, in that they tend to oppose or resist current, connecting inductors in series or parallel will have similar results to connecting resistors in series.
True
True or false: The automobile's ignition system is a common application of inductance in a DC circuit?
True.
True or false: Inductors have different effects in DC and AC circuits
True. Inductors have different effects in AC and DC circuits.
What happens to induced voltage when current is decreasing?
When current is decreasing, the induced voltage tries to keep current constant by using the energy stored in the electromagnetic field while it is collapsing.
What happens to induced voltage when current is increasing?
When current is increasing, the induced voltage slows the current change and the electromagnetic field builds.
What happens when voltage is first applied to a DC circuit?
When voltage is first applied to the DC circuit, the rising current creates an opposing (induced) voltage in the inductor that slows the increase in current.
What does winding the conductor into a coil cause?
Winding the conductor into a coil causes the magnetic field to become stronger.
State the Inductive Reactance Formula
X L = 2πfL
Does coiling a conductor affect the current that flows though the conductor?
Yes, coiling a conductor affects the current that flows through the conductor.
Each level of current flow creates ____________ around the conductor.
an electromagnetic field
A relay consists of switch contacts and a _________________.
coil
An_____________ exists around the inductor, the ___________ of which is proportional to the steady state current level.
electromagnetic field/ strength
The larger the diameter, the _________ the inductive reactance.
greater
The longer the coil, the _____________ the inductive reactance.
greater
What happens if an application requires an inductance value that is not a standard value?
if the inductance value is not a standard value, it may be necessary to combine inductors in series or parallel to achieve the desired value.
The faster the current is changing, the __________________ of the induced voltage.
larger the magnitude of
Induced voltage _____________ the source voltage that is creating the current flow.
opposes
A ___________ is basically an electrically-controlled switch.
relay
If a coil had a turn added to it, its magnetic field would be ____________.
stronger