4 Inductance and Capacitance

What are conditions of Induced voltage?

-Induced voltage is only present when the current is changing - Each level of current flow creates an electromagnetic field around the Inductor - The strength of the field is proportional to that particular level of current.

3 Types of Capacitors

1 - Non-polarized 2 - Polarized or electrolytic 3 - Variable

It takes how many constants to fully charge or discharge the RC circuit?

5

Capacitor

A device that stores electrical energy.

Non-Polarized

Are not polarity sensitive. doesn't matter which way they connect to a circuit.

Inductor in an AC Circuit

Because the current in AC is constantly changing, an Inductor always resist this change. this constant resistance is called Inductive Resistance.

In a DC circuit, a capacitor _________, the current

Blocks

The induced Voltage in an Inductor is only present when current is

Changing

Relay

Device that is basically an electrically controlled switch l. Consists of 2 parts; a coil and one or more sets of switch contacts.

Electromagnets

Devices that use this force to produce some type of output, usually mechanical motion.

A non-conducting material between the plates of a capacitor

Dielectric

______________ capacitors must be connected with respect to polarity.

Electrolytic

Electrons build up on the negative side of the capacitor until the voltage across the plates is ____________ to the source Voltage

Equal

One common application of a capacitor in a DC circuit

Flash of a camera

The letter f in the Inductive Reactance Formula stands for

Frequency

More turns in a coil has Greater or lower inductive Resistance?

Greater

The larger the diameter of the coil the greater or lower the Inductive Reactance?

Greater

The longer the coil, the greater or lower the Inductive Reactance?

Greater

What produces a greater Inductive Reactance an iron core or air core?

Iron core

What happens when you wind the conductor into coils?

It causes the electromagnetic field to become stronger.

In an AC Circuit, a higher frequency means __________ capacitive reactance

Lower

Since the standard unit for Inductance is fairly large, it is usually listed in

Millihenrys

The unit of measurement for capacitive reactance

Ohms

A charged capacitor can be used as I short term _____________ ______________

Power supply

Application of Capacitors in AC Circuits

RF (radio frequency) and AF (audio frequency) filters

Electrostatic Charge

Stationary charge confined to an object

A DC voltage applied to a Capacitor causes a ______________ of electrons on the plate connected to the negative terminal of the voltage source and a _____________ of electrons on the positive side.

Surplus, Shortage

Frequency of the AC current

The higher the frequency of the AC, the greater the reactance. In this respect, Inductive Reactance differs from resistance because the resistance of the resistor is the same at any frequency.

Capacitance

The measure of a device's ability to store electrical energy. The basic unit is the Farad (F)

Purpose of an Inductor

To resist changes in current flow. Often refered to as chokes.

Capacitor Construction

Two conductors (plates) separated by an insulator (dielectric). When Voltage is applied the electrostatic charge is stored in the dielectric.

Time Delay Relay

Use RC timing circuits to obtain a desired delay before they activate.

RC Time Constant

Used to calculate how long a Capacitor will charge. depends on Capacitance and resistance.

RC timing Circuit

Uses a resistor and a capacitor connected in series in a DC circuit to create an electronic timer. possible because the Capacitor will charge at specific rate

____________ capacitors can be adjusted by turning a knob

Variable

Electromagnetism

When electrons flow through wire, an invisible force is created around the wire. This invisible force is called a magnetic field and can be used to do useful such as operate an electric motor. The creation of a magnetic field by the flow of electric current is referred to as electromagnetism.

Inductor effects on charging DC Circuits

When Voltage is first applied to the circuit, the rising current level creates an opposing (induced) voltage in the Inductor that slows the increase in current. Only lasts while the current is rising to it's steady state. After it ahs stabilized, the current through the Inductor is determined solely by the DC resistance of the Inductor.

4 common electromagnetic devices

- Solenoid - Buzzer - Motor - Relay

Variable

Can be adjusted by turning a knob. smaller version are called trimmer capacitor and are adjusted by a screw.

Changing Time delay

Can be changed by adjusting the Capacitance or resistance of the circuit. uses a timer knob.

Example of Inductance application

The fluorescent light fixture uses a special Inductor called a ballast.

Polarized or Electrolytic

Leads are usually marked positive and negative. Provide the most Capacitance in the smallest space and at the least cost.

Inductors in DC circuit

Only affects the circuit when it is turned on/off or when there is a change in the load resistance.

Functions of a Ballast in a Fluorescent light

- It delivers a momentary voltage charge that is higher than the source voltage to the lamp. - It limits the current flowing through the Lamp to a predetermined value.

Capacitor Current effect

When the capacitor is fully charged, the current stops because the charge of the capacitor is equal to the source voltage. Acts like an iron circuit.

2 effects a capacitor has in a DC circuit

- Capacitor charges to a voltage that is equal to the source voltage - The dialectic is an insulator and the voltage potential across the capacitor is equal to the source, a charged capacitor acts like an open and will not allow current to flow in a current.

2 Factors that affect the amount of Capacitive Reactance a capacitor will display

- The Capacitance value - the frequency of the current

3 Factors that determine the Capacitance value of a capacitor

- The are of the plates, the larger the surface are the larger the Capacitance - The distance between the plates, the farther apart the plates are, the less Capacitance will be - The type of dielectric used, some material have the ability to create a stronger electrical field than others, which causes higher Capacitance.

Induced Voltage in relation to current

-When current is increasing, the induced voltage shows the current change an the electromagnetic field builds. - 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. - Have different effects in DC and AC circuits.

5 Factors for Amount of Inductive Reactance

1 - Number of turns in a coil 2 - Diameter of the coil 3 - Length of the coil 4 - Type of core 5 - Frequency of the Alternating Current

Capacitive Reactance in AC Circuits

In an AC circuit, the voltage and current are continually changing, so the capacitor is constantly charging and discharging. The load is then driven by the charge and discharge current from the capacitor because the current cannot flow through the dielectric.

Inductance

A characteristic of electromagnetic devices that opposes any changes in current flow. Is measured in the unit henrys (H).

Inductor effects on Discharging DC Circuits.

If the resistance of a circuit load increases for some reason, the inductor will react. The Electromagnetic field around the inductor collapses, trying to maintain the current at a constant level. After the field's energy is gone, the current remains at this new level until the circuit again changes.

How do inductors work?

Whenever current through an Inductor is changing, a voltage is induced in the Inductor. The faster the current is changing, the larger the magnitude of the induced voltage. This induced Voltage opposes the sources voltage that is creating the current flow. (this is why the induced Voltage is often referred to as counter emf or back emf)