Electronics - Alternating Current and Voltage - Discussion

5. 

A half-cycle average voltage of 12 V is equal to what rms voltage?

[A]. 13.33 V
[B]. 8.48 V
[C]. 18.84 V
[D]. 7.64 V

Answer: Option A

Explanation:

No answer description available for this question.

Ram said: (Mar 23, 2011)  
Imax=Irms/1.414
Imax=1.57*Iav
Imax=1.57*12=18.84
Irms=18.84/1.414
Irms=13.33V

Karuppasamy Kpk said: (Aug 20, 2011)  
RMS value = V(peak value)*.707
V(average value)= Vpk*.637

Therefore, RMS valu =Vav*(.707/.637)

Vrms = 12*1.11 = 13.31= 13.33.

Vid said: (Sep 10, 2011)  
Why we are not directly taken formula for half wave rectifier.

Form factor= (rms/avg).

Abhi said: (May 4, 2013)  
Avg.value = 0.636*Max.value.
Max.value = 12/0.636 = 18.86.

but,

RMS value = Max.value/1.414.
RMS value = 18.86/1.414=13.34.

So, the option is [A].

Kaneez Fatima said: (Jul 12, 2013)  
You all are applying formula for full cycle, but in question we asked to find rms for half cycle. If we apply formula for the half cycle answer may be wrong.

Sunday said: (Aug 27, 2013)  
Can same formula work for rms and half cycle.

Stp said: (Feb 19, 2014)  
Form factor Kf = (rms value/half cycle average value).

Kf for sine wave 1.11.
rms value = 1.11X12= 13.33.

Vinod Semwal said: (Apr 2, 2014)  
Vpick = pai* Vavrag/2.
Vpick = 3.14*12/2.
= 18.84.

Vrms = Vpick/1.414.
= 18.84/1.414.
= 13.33 V.

Engineer Marc said: (Oct 23, 2015)  
This is wrong. If you use full wave formula:

Valve = 2Vpeak/3.1416 => 12 = 2Vpeak/3.14160 (Shift solve).

Vpeak = 18.8496 (full wave).

For full wave Vrms:

Vrms = Vpeak/sqrt 2 = 18.8496/sqrt 2 = 13.13 (Vrms for full wave).

The correct formula for half wave is:

Valve = Vpeak/3.1416 => 12 = Vpeak/3.1416 (Shift solve).

Vpeak = 37.6992.

For Vrms half wave its:

Vrms = Vpeak/2 => 37.6992/2 = 18.84.

Sas said: (Dec 24, 2015)  
For half cycle.

Effective voltage or RMS = 1.11*V average.

= 1.11*12 = 13.32 v.

Kiran V said: (Dec 14, 2016)  
Given;
V avg = 12 V.
Formula taken w.r.f to Full wave rectifier.
Vavg = 2*V max / pi.
Vmax = (V avg * 3.14)/2.
Vmax = (12 * 3.14)/2.
Vmax = 18.84 V.


Vrms = V max /sq.root of (2).
Vrms = 18.84 /1.414.
Vrms = 13.323 V.

Pawan said: (Dec 31, 2016)  
It is, 18.84.

Rahul Yadav said: (Apr 25, 2017)  
Yes, you are correct @Pawn.

Manish Yadav said: (Oct 8, 2017)  
We are not use half wave formula because in electrical method also use full wave formula because in case of electrical we are use in wark 5volt minimum value and more than,
5volt <12volt. So we are useful wave formula.
Iavg.=12volt,
Im=12*3.14÷2=18.84
Irms=18.84÷1.41=13.36.

Lemjr said: (Jan 16, 2018)  
Here, Irms=peak value(Io)/1.41.

Shadan said: (Mar 16, 2018)  
Half Cycle means Half cycle flow in output so it is a half wave rectifier
So avverage voltage of half wave rectifier is =Vm/π.
So Vm =3.14*12,
Vm=26.64,
So rms value of HALF wave is Vm/2,
So 26.64/2=13.33.

Shadan said: (Mar 16, 2018)  
If we talk a Avverage voltage of a complete sine wave then it is 0
So we need to Take Avvg Voltage =0.637*Vm.
Vm = 18.84,
RMS=Vm/√2.
18.84/1.414,
=13.33.

Whis said: (Feb 4, 2019)  
The answer must be 18.85.

Let me explain,
For half wave rectifier:
Vave = Vpk/π
12v = Vpk / 3.14,
12*3.14 = Vpk,
Vpk = 37.699V.

To get rms of half wave rectifer:
vrms(halfwave) = vpk/2.
Vrms(half wave) = 37.699/2.
Vrms = 18.85V.

Muhammad Nouman said: (May 27, 2019)  
Answer is 18.84v.

Explanation:

For Half Wave Cycle Vrms = Vm/2.
and Vm = Vavg x π where π = 3.14 and Vavg = 12v,
So Vm = 12 x 3.14 = 37.68.
and
Vrms = Vm/2 = 37.68/2 = 18.84v.
Vrms = 18.84v.

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