how can the frequency of an alternating current be varied?
346869
In the US, current is set at 60 cycles and in Europe it is 50 cycles, that is the way it is made, I'm not sure you can change that after-the-fact, DC is of course direct.
516677
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.
892848
One of the most frequently used is E=IR    ;E =voltage    I=current   R= resistance. U can change this every way depending on the unknown.\n    Good luck
1009241
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.
971626
Your question isn't clear.\n\nI suspect that what you mean is "how low can I go before I can't do what I want to with the motor".\n\nDepending on the inverter manufacturer, a typical limit is around 7 hertz. This is because reducing the frequency much lower will cause feedback issues and overheating (due to harmonics) in the drive. Also possible is the cycling frequency of the thyristors.\n\nMost applications will prefer low-end frequencies in excess of 12 hertz - to avoid possible tuning/torsional amplification with the structure to which the motor is mounted. No sense trying to run right on a structural resonance point!\n\nPracitacally speaking, there's also an upper limit on frequency as well, usually imposed by the motor design. Often, this is approximately at 2.2 times line frequency (133 hertz for 60 hertz systems, 110 hertz for 50 hertz systems).
740024
By definition, something that has a defined frequency has a period. For the purposes of electricity, alternating current occurs as a sine wave pattern.\n\nThis means that the value of a 60 Hz signal added to a 100 Hz signal gives a waveform that is the compound of the two. Basically, it would appear to be a 160 Hz signal superimposed on a 40 Hz carrier.\n\nThe correct way to determine a value for the signal at any given point in time is to add the values of the two curves based on their frequency ... X sin (pi/3) + Y sin (pi/1.8), where X and Y are the amplitudes of the original two waveforms (X fo 60 Hz, Y for 100 Hz).
199468
(m)\n\nThe electric and magnetic field associated with most electrical appliances and power lines are at the extremely low frequency end of the electric and magnetic spectrum. They have a frequency of 60 cycles per second, or 60 hertz (60 Hz), because the alternating electrical current that creates them changes direction 60 times per second. Radio and television broadcast waves are farther up the electric and magnetic spectrum. Visible light, which is at an even higher frequency yet, is the most familiar form of electric and magnetic energy.
890360
I have already answered part 1. in another question you've asked. I think you probably didn't use the right units (like cm needs to be convered to meters) and got the wrong answer.\n\nNow for part 2:\n\nInduced EMF, ℰ = -L(di/dt)\n\nwhere i is the current and L is the inductance\n\nWe are given that the magnitude of the induced current,\n\ndi = 47 mA\n\nand the oscillation frequency is 100 Hz. This means that dt = 1/f = 0.01 sec\n\nWe have L = 8.44 × 10-^3 henries from before\n\nSo |ℰ| = L(di/dt) = -(8.44 × 10-^3)(0.047)/(0.01) = 0.0397 volts\n\n------------------------------------------------------\n\nNow part 3 has to do with mutual inductance:\n\nVs = VpNs / Np\n\nwhere \n\nVs is the voltage across the secondary inductor, \nVp is the voltage across the primary inductor (the one connected to a power source), \nNs is the number of turns in the secondary inductor, and \nNp is the number of turns in the primary inductor. \n\nTherefore Vp = VsNp/Ns and Vs = 0.0397 volts as calculated before, so\n\nVp = (0.0397)(197)/(2920) = 0.00268 volts
394827
yes you can. For real low freq. you can actually do a DC measurement. Just slow the sweep rate way down and you will see it.
844258
um, basically, there is no connection between resistance and frequency. there are however some circuits that output a frequency based on a time constant that can be set by a resistor though. if that is what you mean, then we need to know what circuit you are talking about.
854524
Radio frequency, or RF, refers to that portion of the electromagnetic spectrum in which electromagnetic waves can be generated by alternating current fed to an antenna
816414
Always the current. The voltage can be whatever.
504604
Time constants in electronic circuits.
742095
Since the impedance of a coil at the 400Hz is higher than it is at 60Hz you can build smaller inductive devices for 400Hz. Weight counts on an airplane. An electric motor or a generator or transformer that produces the same power at a fraction of the weight is a winner when you have to fly it around.\n\nWhy did they pick the exact number 400 I don't know but lately fluorescent lamps are being operated at much higher frequencies so maybe 400 is getting obsolete and will be replaced by a higher frequency too.
844881
if your dealing with simple power supplies that supply DC electronics is pretty simply to get them to run on 50Hz. the first pic is a 60Hz supply....\nhttp://aycu34.webshots.com/image/5353/2000360261420977563_rs.jpg\nall you need to do is add some more capacitance to prevent the ripple voltage from dropping...\nhttp://aycu26.webshots.com/image/4785/2000376600521609993_rs.jpg\n\nbut from the sounds of it, you are dealing with AC electronics. Im sorry I do not have an answer for that.
1177002
yeah you can use a switch (voltage switch) or if you can use binary logic, need to know how much voltage/current you are dealing with
141606
There is an application to convert an AC current to DC.\nAssume that f is a sigmoid function, then integration of\nf^2 over one period gives a constant number which is considered as flattened sigmoid and is analogous with converting AC to DC.