Electronics Engineering

It is simplest form of switching which have dedicated physical path between sending and receiving. In circuit switching network,a set of switches are connected by physical link. A connection between the two stations is a dedicated path made up of one or more links.

AC is supplied to the input of DC power supply. One way to get to DC is to full wave rectify the AC sine wave. Basically you flip the negative side of the AC waveform to the positive side. You are left will all positive voltages varying from the peak voltage to zero and then back to peak. To make DC you need to smooth out the valleys and make them as close to the peak voltage as possible. You do this with various types of filters that usually involve a large capacitor. Once filtered you can use various circuits to either create a fixed DC output voltage or a variable output.

Electrons cannot traverse or move thru an open circuit. Therefore there is no current or 'electron' flow. Voltage may be present with an open circuit but it is doing no 'work'.

Compare an open circuit with 'potential' energy. Even though potential energy exist there is no kinetic energy unless the electrons have a path to take.

An open circuit provides no such path.

Kinetic energy means something with mass is moving and in some cases that movement is harnessed to accomplish 'work'.

Potential (voltage) which is doing nothing because a circuit is open cannot accomplish any work since there are no electrons moving.

Another perspective:

If an electric circuit is opened, the electricity flow stops. This is due to the fact that air is a strong insulator, and most amounts of electricity (save for lightning) do not have enough voltage to overcome this resistance (in a process called ionization). This is reflected in a formula V = I × R where r is resistance, i is amperage, and v is voltage. Through this relationship, as resistance reaches a high level, voltage drops, and the electric flow stops because it cannot overcome the resistance with the force of voltage or amps.

A thought on the ionization process:

As ionization occurs, resistance across the 'gap path' drops and voltage, if not regulated will drop as well. When there is not enough voltage to cause ionization the voltage will be higher than at the time ionization occurs.

At ionization, current (I) will increase, resistance (R) will decrease and voltage (E) will decrease as well and the potential (voltage) is now causing energy or electrons to flow.

As the ionization occurs much less voltage or potential is required to maintain the ionization path than is required to achieve ionization to start with.

Example: A cars ignition coil is capable of producing 45K~50K volts of electricity.

Yet when the voltage is measure at the end of the spark plug wire there will be only 9K or 10K volts due to the air/fuel molecules being ionized

Not to sure ionization actually is applicable to the original question however. :0)

BTW, I'm 'old school' where E=I x R where E = Voltage.

Just like megacycles to megahertz, I guess everything changes but the laws of physics.

Transistor=Transfer+Resistor.

When Transistor operates in active region its input resistance is high and output resistance is low.

So,We can consider transistor as a device which transfers its resistance from high to low.

And by this property transistor amplifies input signal.

It is used to detect very small DC currents only. For AC signals Detectors are used.

The calculations for changing the firing angle in SCR is K = 1 [π − α + 1 sin(2α )]

When a diode passes from forward biased to reverse biased it takes a short period of time for the charge carriers in the vicinity of the junction to recombine and create a nonconducting depletion region. During this time period the diode conducts in the reverse direction, this is called the reverse recovery time.

Its different for every kind of diode, to get the value for a specific diode consult the datasheet.

A passive element is an element of the electrical circuit that does not create power, like a capacitor, an inductance, a resistor or a memristor.

The higher the resistance the dimmer the light will become. The voltage drop (current) is proportional to the resistance as seen in the equation V=IR, since voltage remains the same throughout a series circuit if the equivalent resistance goes up the amount of current reaching the lightbulb must go down to equal the voltage thus creating a dimmer lightbulb.

The formula you are looking for is R = E/I

An open circuit essentially has an infinite resistance. It is shown on digital multimeter as OL. (Open Line) A short circuit should read zero, or nearly zero, depending on the accuracy of the meter.

Watt ( VA or W ) is the unit of power calculated by multiplying the voltage and the Current in Amps. There is no watt in 220 V. But if there is an appliance working with 220V then first find the current it uses and then calculate the wattage the appliance uses.

A trimmer resistor usually called a trim pot is a small variable resistor it is used in circuits to do preset it is trimmed with a trimmer screwdriver it is made up with a round fiber disc with a layer of carbon with a wiper that run on the carbon layer to change the resistance it always have 3 connecting pins where the center one is connected to the wiper and the other two to opposite ends of the carbon strip.

A multistage amplifier is composed of several single stage amplifiers.

Peak - neutral for 120 volts RMS is 169 volts, or 120 * sqrt(2)

Peak to peak will be 2 x this value, or 339 volts.

It is series circuit

Two ways to connect an ammeter, You can use a direct reading type, by connecting the ammeter in series with the load. You can use a current transformer type or CT. The current transformer looks like a wire wrapped donut with two terminals on its side with a hole through the middle. you pass the wire carrying the load through the center. Connect the direct reading meter to the two terminals. A CT type meter allows you to measure higher currents.

The power factor is a measure of the phase difference. If they are exactly in phase the PF = 1. If they are 180 degrees out of phase PF = 0.

Indeed yes. The magnetic core material does have some energy losses associated with its operation. These are known as hysteresis losses, and show up as the magnetic device (transformer, solenoid) becoming warm.

A transformer itself, merely reflects to its primary winding the conditions of the secondary winding. Their resistive losses, their phase change and so on.

This is copied from a similar question to yours fyi.

Using boron, phosphorus, and silicon as examples.

P-type doping is a process where a silicon atom in the lattice is replaced by a boron atom. A Boron atom has 3 electrons in the outer shell, compared with an electron occupancy of 4 for a silicon atom. So a Boron atom provides a vacancy for any free electrons to occupy with a little effort, when an electron chances to be nearby (the four boron-silicon covalent bonds needs 8 electrons to be stable, but only 7 are provided). The net charge of the material is still zero. More about from where the free electron is coming.

N-type doping is using a phosphorus atom to replace a silicon atom. A phosphorus atom has 5 electrons in the outer shell. So a phosphorus atom provides an electron that can be freed with a little effort (the four phosphorus-silicon covalent bonds only need 8 electrons to be stable, each atom needing only to contribute four electrons; the 9th electron will be loosely bound). The net charge of the material is still zero. Where can the electron go?

Magic happens when p-type silicon is brought in contact with n-type silicon to form a pn junction. The excess electron vacancies (holes) in p-Si now can exchange with the excess electrons in n-Si, but the net charge of the p-n silicon entity is still zero. However, microscopically, a depletion region is formed at the pn junction, where excess carriers can cross over to the other side. In the p-Si, excess electrons from the n-Si start filling up the holes (the lack of the 8th outer-shell electron to form the four stable boron-silicon covalent bonds) and negatively-charged boron atoms are formed. In the n-Si, excess holes from the p-Si start swallowing up the loosely-bound electrons (the 9th electron in the outer shell) of phosphorus atoms and positively-charged phosphorus atoms are formed. Once formed, and in the absence of an electric field, the depletion region now presents an energy barrier to any further carrier movement and a steady state results -- no net current in the pn junction.

An insulator is a material that prevents the passage of electricity. An example is the plastic insulating cover on electrical wires,

A conductor is a material that allows electricity to flow. An example is the copper wire used inside electrical cables.

a transformer require AC to function as desired it transform the AC to different levels. DC on a transformer can only see the actual primary or secondary resistance if the source is not limited in current it will burn the transformer by excessive heating since it will see only wire resistance.

Answer 2

the application of an AC voltage, V on one winding of the transformer produces alternating flux that links the entire core of the transformer. The changing flux induces an emf, E that opposes the main voltage. the current through the winding in this case is {(V-E)/R}; R= winding resistance

in case of application of DC, since there is no changing flux, there is no induced emf and hence the current will be V/R

since the resistance of the winding is very small, the current is very high and this can burn away the windings. hence DC is not used.