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Why we use rms value of current why not simple value of current?
Wiki User
∙ 11y ago
RMS (root mean square) is often used as opposed to the peak to peak value because it expresses the actual power for AC systems. For example, your actual home voltage is closer to 170 volts peak - neutral. Say you have 1/2 Amp peak -neutral current flowing. Actual power is equivalent to:
P = Vrms*Irms; RMS = Vpeak-neutral/sqrt(2)
P = 1/2 * (Vpeak-neutral) * (Ipeak-neutral).
You can quickly see that discussing wire size, fuse sizing, breaker sizing, etc. in terms of peak - neutral or peak- peak volts / currents, will quickly become more complicated than it needs to be.
This is also a more useful value from a usage standpoint, as you will be charged for the power you use.
Wiki User
∙ 14y ago
Wiki User
∙ 11y agoThe root mean square value of an alternating current is the value of alternating current that will do the same amount of work as a given value of direct current. For sinusoidal currents, this works out at 0.707 times its amplitude or peak value. Since voltage and current are proportional to each other, this also applies to alternating voltages. Root mean square values, therefore, provides a way of comparing a.c. and d.c. values.
Wiki User
∙ 11y agoThere is no such thing as 'alternative voltage'! The term you want is 'alternating voltage'.
The average value of an a.c. voltage or current over a complete cycle is zero, so it is not very useful to think of a.c. in terms of average values. Instead, we look at its 'heating effect' of the a.c. current, and compare it with the heating effect of a continuous, d.c. current. If a current of say, 10 A d.c. produces a particular heating effect, then an a.c. current of 10 A (rms) will result in exactly the same heating effect. This is why 'rms' values are also called 'effective' values, as it has exactly the same effect as a d.c. current of the same value.
Wiki User
∙ 11y agoThe RMS value is a representation of the DC equivalent of an AC current.
Thinking of electric current as water flow is generally a great way to visualize how most things electronic work.
In this case, the water is flowing in waves, sometimes it's moving fast (higher voltage) sometimes it's moving slow, sometimes it even moves backwards (the negative voltage part of the AC cycle).
Well that's all well and good but how much force the water flow has for practical purposes (its voltage) is important to be able to estimate, and that's why RMS is used.
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Why it is useful to use rms notation for alternating current and voltage?
AC waveform is sinusoidal waveform it has both positives and negative cycles so we dont have a standard constant value to do Measurements so instead of using AC quantities we use ROOT mean square values which is obtained by dividing Vpp(peak to peak voltage) by 1.414AnswerThe rms-value of an AC current is the same as as the value of DC current that will do the same amount of work. For example, 10 A (rms) AC will do exactly the same amount of work as 10 A DC.
How do you measure rms value of complex waveform?
rms value is measured using voltmeter with the use of heat sensing elements.
What is the difference between rms value and average value of AC?
rms value of ac power = dc power in reference to heat production in pure resistive load So ac power of some rms value will produce the same heat in resistive load as dc power will of same value
Can you use ac volt on a DC volt?
There is no such thing as a d.c. transformer; all transformers work on a.c. So, what you are probably referring to is a power supply: the type of thing you would use, for example, to run a small radio or to charge a battery. In that case, no, you cannot plug a a.c. appliance into a power supply that has a d.c. output.
Why ac voltage of inverter measures 95.1 volts?
Because inverters do not produce a pure sinewave AC and you did not use a True RMS digital meter to measure the voltage.Meters that are not True RMS actually measure the average, then display the value on a scale that assumes the input is a pure sinewave showing what the RMS would be for that average. For waveforms significantly different from sinewaves (as the inverter produces) that displayed value can be seriously wrong.
Why it is useful to use rms notation for alternating current and voltage?
AC waveform is sinusoidal waveform it has both positives and negative cycles so we dont have a standard constant value to do Measurements so instead of using AC quantities we use ROOT mean square values which is obtained by dividing Vpp(peak to peak voltage) by 1.414AnswerThe rms-value of an AC current is the same as as the value of DC current that will do the same amount of work. For example, 10 A (rms) AC will do exactly the same amount of work as 10 A DC.
How do you measure rms value of complex waveform?
rms value is measured using voltmeter with the use of heat sensing elements.
Why to use rms value for ac?
An r.m.s. value of a.c. current does exactly the same amount of work as a corresponding value of d.c. current. For example, 10 V (rms) a.c. is exactly equivalent to 10 V d.c. Since voltage and current are proportional to each other, then an r.m.s. value of a.c. voltage is exactly equivalent to the corresponding value of d.c. voltage.So, r.m.s. provides a way of equating a.c. and d.c. values.
Which has a higher RMS value given a sine wave a square wave and a sawtooth wave?
A square wave has the highest RMS value. RMS value is simply root-mean-square, and since the square wave spends all of its time at one or the other peak value, then the RMS value is simply the peak value. If you want to quantify the RMS value of other waveforms, then you need to take the RMS of a series of equally spaced samples. You can use calculus to do this, or, for certain waveforms, you can use Cartwright, Kenneth V. 2007. In summary, the RMS value of a square wave of peak value a is a; the RMS value of a sine wave of peak value a is a divided by square root of 2; and the RMS value of a sawtooth wave of peak value a is a divided by cube root of 3; so, in order of decreasing RMS value, you have the square wave, the sine wave, and the sawtooth wave. For more information, please see the Related Link below.
What is difference between RMS and true RMS?
RMS means root mean square and watts means power. What a difference! Scroll down to related links and look for a neat pressure converter at"Root Mean Square" und knowlege about "Watt" Watts root mean square is the effective value of alternating current electrical power compared to direct current power. Scroll down to related links and look for "Why there is no such thing as 'RMS watts' or 'watts RMS' and never has been". RMS watts is meaningless, but we use that term as "an extreme shorthand" for power in watts calculated from measuring the RMS voltage.
Convert ac voltage rms to dc voltage?
The dc voltage of a rectified ac voltage will be the peak value of the ac voltage less the forward voltage drop of the diode.The rms voltage of a sinusoidal ac voltage is sqrt(peak) / 2, but you also have to consider if the ac voltage is balanced around zero.For a normal US house voltage of 117VAC, the peak voltage is about 165V, or 330V peak to peak. Your dc voltage is then around 164V.Run that rectified voltage through a capacitor, and you will still have 164V peak value, but the voltage over time will dip because the capacitor will discharge during diode off time, and recharge when it turns back on.AnswerA given value of a.c. rms voltage is exactly equivalent to the corresponding value of d.c. voltage. For example, 120 V (rms) is exactly equivalent to 120 V d.c. This is why the alternative name for 'rms voltage' is 'effective voltage'. This is based on the fact that a current of, say, 10 A (rms) will do exactly the same amount of work as a d.c. current of 10 A. And, of course, voltage and current are proportional.
A resistor of value 20 ohms is connected across an ac supply of 110 volt 50 hz what will be the total current following the circuit?
Current = (voltage) / (resistance) = 110/20 = 5.5The current will be 5.5 Amperes RMS, alternating at 50 Hz.Note:If you try this at home, you must use a gigantic "power" resistor.The resistor dissipates E2/R = I2R = 605 watts RMS !
What is the peak value of current if its rms value is 2A?
If an AC current is sinusoidal, then the peak value of a current with an RMS value of 2A is 2.8A, or 2A times the square root of 2.However, very few current waveforms are sinusoidal. In fact, they are often far from sinusoidal - they are more often pulsating - because most power supplies, even switching power supplies, only draw current when the rectifier diodes conduct to recharge the primary filter capacitor. That only occurs once (half wave rectifier) or twice (full wave rectifier) each line cycle.The square root of 2 rule does apply if the load is purely resistive and the voltage is also sinusoidal. Most voltages are also not sinudoidal, because of the pulsating current issue, and because conductors are not perfect zero impedance conductors. Voltage waveforms, however, are more closely sinudoidal than current waveforms.The most accurate way to measure the peak current value is to observe it with an oscilloscope. If you want the analytic approach, you need to back calculate from peak value to RMS value, knowing that RMS value is the square root of the sum of the squares of the observations divided by N, as delta T approaches zero, and N approaches infinity. (Best to just use the oscilloscope.)
How do you measure effective value of an alternating voltage?
The "effective" value of an alternating voltage is generally considered to be the RMS (Root-Mean-Square) value. The best way to measure that is with a True RMS voltmeter. Lacking that, if the voltage is sinusoidal, you can use an older style peak measuring voltmeter that estimates RMS value by dividing internally by the square root of 2. Any other shaped waveform will be measured incorrectly, depending on the amount of deviation from sinusoidal. (Square wave is the best example of error in this case - RMS and peak should be the same, but they won't read the same except on a True RMS voltmeter.)
Why you use 0.707for rms values?
reciprocal of the square root of 2, converts from peak voltage to rms voltageAnother AnswerThis figure results when you work out how much work is done by one complete cycle of a.c. current. Since work is proportional to the square of a current, if you divide one complete cycle of a sine wave current into lots and lots of instantaneous values, square each of these values, find their average (mean) value, then find the square root of that value, you will have found the 'root-mean-square' of the current over a complete cycle. This value always works out to 0.707 x the peak or maximum value of the sine wave. For other waveforms, other r.m.s. values result.
What is the difference between rms value and average value of AC?
rms value of ac power = dc power in reference to heat production in pure resistive load So ac power of some rms value will produce the same heat in resistive load as dc power will of same value
Can you use ac volt on a DC volt?
There is no such thing as a d.c. transformer; all transformers work on a.c. So, what you are probably referring to is a power supply: the type of thing you would use, for example, to run a small radio or to charge a battery. In that case, no, you cannot plug a a.c. appliance into a power supply that has a d.c. output.
