When a sinusoidal a.c. passes through the primary coil of a transformer, it sets up a changing magnetic flux which induces an emf in the secondary coil.  What is the phase difference between these three quantities: a.c., magnetic flux and induced emf?  I need to draw three graphs showing these relationships.
204849
from my knowlege the emf is opposite of the direction of change of flux and the difference between ac, emf is the phase constant. for example if emf is vertical ac is 90degrees-phase constant
375713
in a CE amplifier, when base voltage increase, base current increases. It causes an increase in collector current also. The collector current causes a voltage drop in the collector resistor. Because the output is situated below the collector resistance (with reference to Vcc) the output voltage will decrease as voltage drop across collector resistor increase. Thus it produces a 180 phase shift. (input positive, output negative and vice versa)\n\nYou can verify with this equation: Vcc=IcRc+Vc  (Vc=Vout)\nWhen  Ic increase, Vc must decrease because Vcc is constant.\n\nYou can analyze CB and CC circuits using the same manner by writing the voltage drop equations along a line or a loop. Then find the relation between input voltage and output voltage. You will see that there is no phase shift. (Input increase, output also increase)
322336
hi,\n\nas i understand it, the way a DC-DC converter operates is in 3 stages:\n\nfirst, V_in is used to drive a pair of coupled transistors (or some other oscillatory circuit) that output a square wave or some kind of time-varying oscillatory voltage.\n\nsecond, that AC signal is used to drive a transformer which consists of two inductors.  the ratio of the number of turns in the primary and secondary windings of the transformer determines the step-up or step-down ratio of the transformer.  if you have a 3:1 inductor then you will step down the voltage by a factor of 3, for example.\n\nthird, the transformed AC signal gets converted to DC by a bridge rectifier or some other AC->DC circuit.  generally speaking, a bridge will output a DC voltage that is simply proportional to whatever AC you put into it.  (of course if you way over- or under-drive it, it won't work right.)\n\nanyway, if you have a single missing turn on either side of your transformer, that will change the step-up/down ratio.  my 3:1 example would become a 2:1 transformer and then you'd get an output voltage that was too high (1/2 of the input, instead of 1/3).  \n\nthen the rectifier will just flatten out whatever voltage you put into it.\n\nhope this helps!
280090
The difference lies in the nature of the fields. The electric fields can affect every charged particle whether it is static or moving but magnetic field can affect it only if its moving that even not along the magnetic field lines. The force due to electric field follows F=qE and is in the direction of the field itself whereas the magnetic force follows F=q(vxB) and is in the perpendicular direction to the magnetic field and thus causes the charge particle to gyrate around the field lines. Moreover the work done by a magnetic force is zero unlike in the case of an electric force.
375037
Stray voltages/currents between grounded metal parts is caused by a difference in resistivity. Usually, it is because the ground rod has a greater resistivity than the metal parts connected to the water/drainage/gas system.\nAgain as has been said on other occasions in this forum, Ohm's Law comes into play..... Current is equal to voltage divided by resistance. So if there is a differing resistance between the two systems AND there is a low resistance path betweeen the electrical wiring and earth on an appliance, current will flow (continuously) to the frame of the appliance and to ground. So if current is flowing to ground and the appliance ground has a higher resistance to earth than the ground of the adjacent metal parts there will be a difference in potential between the two. This is often felt as a tingling sensation --- The reason why it doesn't trip the breaker is that the current flow is lower than the trip setting of the ELCB (earth leakage circuit breaker). It does not have anything to do with "Back EMF" back EMF is the voltage generated in a dc motor that limits the amount of current that can pass through the armature windings.......\n\nIf you have this problem, GET AN AUTHORIZED ELECTRICIAN TO INVESTIGATE AND CORRECT THE PROBLEM IMMEDIATELY. It certainly is a dangerous situation that can cause death.\n\nSource: Electrical Engineer (ret) with 45+ yrs experience.
394516
what's a flux capacitor?
89816
The secondary voltage is determined by the ratio of turns on the primary versus the number of turns on the secondary.\n\nN1 = Number of turns on the primary\nN2 = Number of turns on the secondary\nn  = Ratio of turns = N1 / N2\n\nV1 = Voltage of the Primary\nV2 = Voltage of the Secondary\n\nV1 = V2 x n    or    V2 = V1 / n \n\nThis only works exactly in an "ideal transformer"  There are, of course, resistive losses, coupling losses, etc. that will affect the final numbers in the real world.
373322
For three phase AC powered loads, three separate power lines provide power to the load. The voltage waveforms on these three lines differ only in their timing, or phase relationship. A fourth wire may provide a neutral connection to the load. In the case of balanced loads, where the current in each of the three phases is equal, the current in the neutral wire will be zero. The neutral wire may therefore be eliminated, as it is not necessary for the purpose of carrying current. The vector sum of the currents drawn from the three phase lines will be zero with a balanced load. A non-zero sum of the current indicates an unbalanced load and that a current is returning to the generator, or current source, via an unintended path. This is the ground fault current.\n\nThe ground fault current for a three-phase system, without neutral, may be measured by performing a vector summation of the phase currents. This summation may be performed by a current sensing transformer with the phase currents passing through the common aperture in parallel. The magnetic field induced in the transformer core is then the vector sum of the three individual phase currents and the voltage induced in the secondary winding placed on the transformer provides a signal representing the vector sum of the currents, the ground fault current.\n\nThe electrical characteristics of ground faults in solidly grounded WYE systems allow for simple detection of ground currents by monitoring the phase and neutral currents for a simple unbalance in those currents. The principle is that the current going to the load on the normal phase and neutral conductors should return via those same conductors. Any missing current is deemed a fault to ground on the load side of the detector and, when that unbalance exceeds a set threshold, a ground fault is determined. The basic ways of measuring this unbalance for solidly grounded four-wire systems use one ground sensor surrounding the phase and neutral conductors, four individual current transformers connected in a WYE configuration, or four voltage sources connected in a delta configuration.
534783
The earths magnetic field is static, but an Alternating Current source will fluctuate, reversing its  North-south polarity 60 times a second.\n\nThe affects of fluctuating magnetic fields are very different from the effects of a fixed field.\n\n"A strong changing magnetic field can induce electrical currents in conductive tissue, such as the brain. Since the magnetic field will penetrate tissue, it can be generated outside of the head to induce currents within, hence Transcranial magnetic stimulation. These currents will depolarize neurons in a selected part of the brain, leading to changes in the patterns of neural activation."\n\nSee the link below for more details:
332910
The terms refer to current direction.\n\nDC (direct current) only travels in one direction.\nAnything operating from a battery  (flashlight, car starter, disc man) is running on DC current.\n\nAC (alternating current) changes direction at a regular frequency. In North America, that's 60 times a second, or 60 hertz. Electrical outlets supply AC current for most household appliances.
233324
Ripple is the voltage change in regulated Alternating Current.  \n\nIt sounds like you're working with a bridge rectifier setup, and when the input AC changes (starts going negative after peak) the rectified voltage will begin to drop, until the next cycle brings it positive again.\n\nWhat you will end up with is a scalloped waveform of AC, instead of a sine wave.  Capacitors can be added to the circuit to limit ripple.  They will feed some of their stored charge into the circuit as the AC voltage drops, to keep the wave as flat as possible.\n\nIf you have more questions about this feel free to contact me directly.
56095
Electromagnetic waves??? thats something ive never heard of before. how about posting the article or the website online? \n\ni do know that electricity can be "transmitted" by magnetism, via electromagnetic induction. according to faraday's law, a changing rate of magnetic flux linkage induces an electromotive force, and thus induces current on a conductor. check out faraday's law at wikipedia for more info dude...
366478
we know that for power, P=IV. we also know that whatever power goes into the transformer comes out of the transformer(conservation of energy). this means that V is inversely proportional to I. or I is inversely proportional to V.\n\nif you already know how much V was stepped up, then just step down the I by the same ratio. for eg, if 110V 10A was transformed to 220V, then the step up ratio is 2. therefore current is stepped down by 2. so current will be 5. try equating 110x10 with 220x5, it is constant.\n\nall of this assumes that the transformer is 100% efficient. if there are losses due to heat, then you multiply the exit current by the efficiency factor. eg, if the trans is said to be 80% effiecient, then the actual exit current would not be 5A but 4A. voltage is not affected by effiency issues.\n\nby the way transformers only work with AC, the guy who mentioned direct currents is thinking of current rectifer not transformer.
231690
The RMS (root-mean-square) value of AC voltage is NOT dependant on the frequency.  For a sine wave, it is .707 (half the square root of 2) multiplied by the peak voltage.\n\n120 and 240 volt circuits common in the US are derived from the center-tapped transformer, the center called the neutral.  This gives you 120V between each phase and neutral, and 240V between the phases.  An analogy that might make more sense is with batteries.  You can put two 9V batteries in series to get 18V, but you still have 9V across each battery.\n\nI think what you want to know from your question, is why do we have both 120V and 240V.  You can argue 120V is safer than 240V, but it is more historical that 110-120V is used in the US (many other countries, but not all, use 220-240V).  The reason for having 240V for some equipment is with a higher voltage it will draw less current, so smaller wires can be used.  Similar to power transmission using high voltages.\n\nThe safety ground, the 3rd round pin on a normal plug, is connected to the neutral at the electrical service.  The neutral is grounded (to the earth), and so is the safety ground, but that connection to the earth has nothing to do with its purpose.  This safety ground connects metal parts of equipment to the neutral, so if a fault in the equipment causes voltage on those metal parts, it will trip the circuit breaker rather than give you a shock (if you were touching it WHEN the fault occurred, you could get a shock before the circuit breaker tripped).  Another thing about the safety ground, it never carries current under normal conditions, and for that to be true it can only be connected to the neutral at the service.  NEVER connect a safety ground to a neutral at another point.\n\nAlso, never take the cover off your circuit breaker or fuse panel if you don't know what you are doing.  Suggesting someone take off the cover and poke around with a fluke is a bad idea.
191171
flux are field lines. In reference to the electric motors... when electric current flows through a wire placed in a magnetic field, the wire moves in the direction perpendicular to the magnetic flux and also to the direction of electric current.\n\nIn reality flux lines are "imaginary". They were used by Michael Farady to explain electric and magnetic field lines.
163496
DC is Direct Current in which the electrons move in one direction through the wire all the time.\nAC is Alternating Current in which the electrons flow one way for a short time and then switch directions and flow the other way for a while.\nThe constant direction switching does not interfere with the work the electricity does if the devices using it are properly designed. Some devices, like incandescent light bulbs, work equally well with either type of current. Other types of devices, like transformers, depend on the constant switching to operate.
4793
The power factor of an AC electric power system is defined as the ratio of the real power to the apparent power.\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 alternative 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:\n\n. \nIn the case of a perfectly sinusoidal waveform, P, Q and S can be expressed as vectors that form a vector triangle such that:\n\n \n\nIf φ is the phase angle between the current and voltage, then the power factor is equal to , and:\n\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