What is power factor in ac circuits?
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The power factor of an AC electric power system is defined as the ratio of the real power to the apparent power.\n\nExplanation\n\nIn a purely resistive AC circuit, voltage and current waveforms are in step, changing polarity at the same instant in each cycle. Where reactive loads are present, such as capacitors or inductors, energy storage in the loads result in a time difference between the current and voltage waveforms. Since this stored energy returns to the source and is not available to do work at the load, a circuit with a low power factor will have higher currents to transfer a given quantity of power than a circuit with a high power factor.\n\nReal power is the capacity of the circuit for performing work in a particular time. Due to reactive elements of the load, the apparent power, which is the product of the voltage and current in the circuit, will be equal to or greater than the real power. The reactive power is a measure of the stored energy that is reflected to the source during each alternating current cycle.\n\nAC power flow has the three components: real power (P), measured in watts (W); apparent power (S), measured in volt-amperes (VA); and reactive power (Q), measured in reactive volt-amperes (VAr).\n\nThe power factor can be expressed as:\nP/S\nIn the case of a perfectly sinusoidal waveform, P, Q and S can be expressed as vectors that form a vector triangle such that:\nS*S=P*P+Q*Q\n\nBy definition, the power factor is a dimensionless number between 0 and 1. When power factor is equal to 0, the energy flow is entirely reactive, and stored energy in the load returns to the source on each cycle. When the power factor is 1, all the energy supplied by the source is consumed by the load. Power factors are usually stated as "leading" or "lagging" to show the sign of the phase angle.\n\nThe power factor is determined by the type of loads connected to the power system. These can be\n\nResistive \nInductive \nCapacitive \nIf a purely resistive load is connected to a power supply, current and voltage will change polarity in phase, the power factor will be unity (1), and the electrical energy flows in a single direction across the network in each cycle. Inductive loads such as transformers and motors (any type of wound coil) generate reactive power with current waveform lagging the voltage. Capacitive loads such as capacitor banks or buried cable generate reactive power with current phase leading the voltage. Both types of loads will absorb energy during part of the AC cycle, only to send this energy back to the source during the rest of the cycle.\n\nFor example, to get 1 kW of real power if the power factor is unity, 1 kVA of apparent power needs to be transferred (1 kVA = 1 kW × 1). At low values of power factor, more apparent power needs to be transferred to get the same real power. To get 1 kW of real power at 0.2 power factor 5 kVA of apparent power needs to be transferred (1 kW = 5 kVA × 0.2).\n\nIt is often possible to adjust the power factor of a system to very near unity. This practice is known as power factor correction and is achieved by switching in or out banks of inductors or capacitors. For example the inductive effect of motor loads may be offset by locally connected capacitors.\n\nEnergy losses in transmission lines increase with increasing current. Where a load has a power factor lower than 1, more current is required to deliver the same amount of useful energy. Power companies therefore require that customers, especially those with large loads, maintain the power factors of their respective loads within specified limits or be subject to additional charges. Engineers are often interested in the power factor of a load as one of the factors that affect the efficiency of power transmission.\n\n\nNon-sinusoidal components\n\n\nIn circuits having only sinusoidal currents and voltages, the power factor effect arises only from the difference in phase between the current and voltage. Th
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AC stand for alternating current.  AC current can oscillate at whatever frequency (# times per second, usually expressed in Hertz, Hz) you want it to.  However, the power that comes into your house oscillates at 60 in the US and 50 in Europe.  This has to do with the development of electricity.  They had to sync up the phases when they created it and they would do this by hooking up the two sources to lightbulbs that would flash at each peak.  50 or 60 times a second is about the maximum cycle rate visible by the human eye.\n\nPositive and negative current denote which direction electrons are flowing.\n\nNothing will happen if you touch positive or negative current, just don't touch both at the same time.
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No.  The skin effect will cause the AC resistance to be higher than the DC resistance.  This difference is larger for higher frequencies and for larger wires.
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For a simple answer frequency applies only to alternating current.\n\nIf you want to get more technical then DC can have frequency if you use something like a thyristor (SCR) to produce stepped DC.  But this is used for simulating AC when you are using a load that requires AC and DC. An example of this would be  the control circuit for a reluctance motor.
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Most house circuits are rated at 15 amps and the units you have found that list 115 volts, 15 amps are likely designed for such circuits.  That said, you must consider the total amps of other loads on the same circuit which may serve several other wall outlets, etc.  It is not a good idea to run other major units such as TV's or refrigerators on the same circuit serving your air conditioner.  Perhaps you can share the circuit with a clock or small lamp.  The air conditioner may draw maximum amps only during startup of the compressor (you can hear it groan).  If the circuit trips, shed other loads.  Avoid using extension chords for the air conditioner (even heavy duty chords increase voltage drop at the plugs).  One neighbor discovered that his house voltage was often lower than it should be and the power company added a booster for him.  Low voltage draws more current (amps).  A qualified electrician may be able to upgrade your circuit to 20 amps, depending on the house wiring, to avoid trips.  Good luck.
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acrtoss the power supply
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Power electronics is the technology associated with the efficient conversion, control and conditioning of electric power by static means from its available input form into the desired electrical output form.
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If it's for a simple hobbyist application they need to know only the resistance value and its power rating.\n\nA full specification would also include:\n\ntolerance,  thermal coefficient,  maximum voltage.
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In D.C circuits current flow is  always  in one direciton.\nIn A.C circuits current is fluctuating that is changing its direction periodically, say 50 times per second or 60 times per second. But in A.C when the current is switched off suddenly in some circuits having coils and condensers there will be back emf and sparks will be prduced in the switching system. Normally the device is manufactured taking this into account.
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AC & DC of the same voltage can push the same amount of current through a wire.  In regular use however, we never see them at the same voltage.  There is no DC power transmission, and no one makes AC batteries.\n\nYour portable stereo either has an adapter to lower the 120VAC house voltage & convert it to DC, or has circuitry to raise your 12VDC car voltage & convert it to AC.  The former is more likely.  Since homes have 120VAC power, most appliances that use lower voltage DC have adapters, either built-in or external.
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The answer is in your last statement: "as long as its the only component in the circuit".  The fact is the wire is only one of three resistances in your circuit; you also have the resistance of the ammeter (and the wires connecting it to the circuit) and the output impeadance of the power pack (and the wires connected to it).  \n\nSo, your actual circuit is really a voltage divider.  The voltage across the constantan wire is going to be:\n\nOC_Voltage x R_C / (R_C + R_E)\n\nWhere OC_Voltage is the open circuit voltage of the power pack, R_C is the resistance of the Constantan, and R_E is the resistance of everything else.
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AC (alternating current) can be transformed into a DC (direct current) by means of a rectifier or bridge rectifier circuit depending on the AC circuit.\n\nA single AC line to ground or common an be rectified by the use of a single diode. This is a crude dc circuit.\n\nUsing a dual AC line, not grounded, where there are two lines, both above ground, then a full wave bridge rectifier can be used. Four diodes are used which rectify both the positive half as well as the negative half of the AC waveform.\n\nThen there is the 3phase rectifier bridge which uses 6 diodes, converting 3 AC lines, they are 120^deg outof phase of each other. Most industrial machines are using 3 phase power.\n\nMachines using this 3 phase power usually have a Motor Control Center which house a AC Drive (AC to DC to AC) inverter. This drive uses devices called IGBT which are active diode devices providing controlled amounts of power at variable frequency to run a machine.\n\nTo smooth out the DC waveform a capacitor bank is attached to the output of the DC bridge rectifier. \n\nAs you drive by an industrial park you will notice three power lines usually connected to each building. This is the 3 phase power. \n\nLarge Hybrid electric vehicles use such machines.
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Think about the simpliest capacitor. It is clear that two metal plates that don't touch won't let a DC current pass, right? But the spacing is very thin so that the plate's charges can effect one another. When you first put current (even DC) to a discharged capacitor, it charges up and for a brief time it does conduct current. How long? Well it will charge to 2/3 of the total voltage in RC seconds (where R is the resistance of the circuit). So when AC current is "fast" enough, the cap is constantly in a charge/discharge state and current flows. The effective resistance (reactance) of the cap is 1/(2*pi*F*C). So the resistance goes down as the capacitance and the frequency rises.\n\nThe inductor, on the other hand is just a coil of wire. Again, it is easy to imagine that it will conduct DC. But when you first apply current (even DC) to a coil, the magnetic field will interact with the coil and produce an opposing voltage. This only occurs when the magnetic field is forming or collapsing (remember, magnetic fields that do not move do not produce electricity). So right when you change the current, the inductor will "resist" the change, but if the current doesn't change, it is just a wire. The reactance of a coil is 2*pi*F*L, so the resistance increases with frequency and inductance.\n\nNow, combining inductors and capacitors is another interesting subject, but you didn't ask about that....
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Diodes convert ac to dc.  You need an inverter to convert dc to ac.  That's done with a timer circuit and powerful transistors.
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light bulb is the load. conductor would be the way to get the power to the load and other devices , the switch is the way to stop and start the flow of current, the insulator will keep the power from leaving its proper path, the ammeter will tell you how fast the power is being used in amps , volt meter will tell you what the pressure of the power is in volts, the battery is your storage of power.
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Electron flow in the circuit (outside the battery) is from - to +\nHole flow in the circuit (outside the battery) is from + to -\n\nPower in an electric circuit is defined as:\n Watts = Amps x Volts\n\nis equivalent to:\n <power> = <current> x <potential, voltage>\n\nis equivalent to:\n P = I x E\n\nSince one cannot have a non-zero value for power without flow(current), then you could say it comes from both - and + being applied to a load.
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I recently read about new power strips that cut even standby power to equipment that are plugged into them. For example, your computer and printer still draw a current even if shut off. this tricle can add up over the course of a year. These power strips cut off that tricle until the moment the unit is roused from standby.\n\nThis was in a pretty good article in this month's Kiplinger's Personal Finance magazine.