Register to reply

Peak value or rms?

by leolaw
Tags: peak
Share this thread:
leolaw
#1
Apr6-05, 01:57 AM
P: 86
I am always confused with rms value and peak value, so here is the problem:

What will be the peak value of the current of a well-insulated [tex]0.03\mu F[/tex] capacitor connected to a 2.0-kV(rms) 720-Hz line?

So first I find the reactance of the capacitor, which is:
[tex]X_c=\frac{1}{2\pi fC}[/tex]
[tex]7.4k \Omega[/tex]

and then [tex]V_{rms} = I_rms * X_c[/tex]
[tex] 2*10^3 = I_{rms} (7.4 * 10^3)[/tex]
[tex] I_{rms} = 2.7 * 10^{-1} A[/tex]

so is this the right answer, or do i have to multiply it by [tex]\sqrt{2}[/tex] to get the peak value?
Phys.Org News Partner Science news on Phys.org
Hoverbike drone project for air transport takes off
Earlier Stone Age artifacts found in Northern Cape of South Africa
Study reveals new characteristics of complex oxide surfaces
ehild
#2
Apr6-05, 02:49 AM
HW Helper
Thanks
P: 10,350
Quote Quote by leolaw
I am always confused with rms value and peak value, so here is the problem:

What will be the peak value of the current of a well-insulated [tex]0.03\mu F[/tex] capacitor connected to a 2.0-kV(rms) 720-Hz line?
....
[tex] I_{rms} = 2.7 * 10^{-1} A[/tex]

so is this the right answer, or do i have to multiply it by [tex]\sqrt{2}[/tex] to get the peak value?

The peak value is sqrt(2) times the rms value, and the peak was asked....


ehild
thomate1
#3
Apr6-05, 03:29 AM
P: 49
Yes he is correct. Since current can be described in the form of a sin fn, the maximum amplitude obtained is known as peak value. rms value is the root mean square value of all individual values

For eg, peak value of sin(x) is 1. But it takes values from -1 to 1. rms value=1/sqrt(2).
It is the net effect.


Register to reply

Related Discussions
The party's over: peak oil has distracted us from peak helium! General Discussion 11
Peak Oil Earth 15
Peak Oil General Discussion 2
Peak Oil Current Events 24
Peak Oil General Physics 0