# Electronics - Alternating Current and Voltage - Discussion

Discussion Forum : Alternating Current and Voltage - General Questions (Q.No. 5)
5.
A half-cycle average voltage of 12 V is equal to what rms voltage?
13.33 V
8.48 V
18.84 V
7.64 V
Explanation:
No answer description is available. Let's discuss.
Discussion:
24 comments Page 2 of 3.

Manish yadav said:   7 years ago
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.

Rahul yadav said:   7 years ago
Yes, you are correct @Pawn.

Pawan said:   7 years ago
It is, 18.84.

KIRAN V said:   7 years ago
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.

SAs said:   8 years ago
For half cycle.

Effective voltage or RMS = 1.11*V average.

= 1.11*12 = 13.32 v.

Engineer Marc said:   9 years ago
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.

Vinod semwal said:   1 decade ago
Vpick = pai* Vavrag/2.
Vpick = 3.14*12/2.
= 18.84.

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

Form factor Kf = (rms value/half cycle average value).

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