Progress is impossible without change; and those who cannot change their minds cannot change anything.
..."George Bernard Shaw(1865-1950, Irish dramatist, essayist and critic, Nobel Prize for Literature 1925)"

Reply #1 on: September 14, 2010, 04:23:26 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

i always wanted to make this!

My input to the applet. corrected some typo for the applet. added some design to the layout added omega w

comment! good work prof hwang this applet will be a good tool for student learning, they usually cannot understand the transformation of the curve from "A*sin(w*t)" to ("A*sin(w*t)")^2 as this applet aims to visually represent.

question, how do you use the blue "B-A*A*cos(2*w*t)/2" to allow learning of average power in AC circuit calculation?

my teaching approach i normally use only the red curve "A*sin(w*t)" and the black curve "A*A*sin(w*t)*sin(w*t)" only.

other student learning difficulty and suggestion for applet ? the other part is the area under the curve "A*sin(w*t)" to ("A*sin(w*t)")^2 is half of the rectangle form by A*A and the period T. student cannot visualize this i feel. i guess i could use Ejs data tool to find area under the curve to show that.

Reply #3 on: September 14, 2010, 11:42:11 pm » posted from:,,Taiwan

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other student learning difficulty and suggestion for applet ? the other part is the area under the curve "A*sin(w*t)" to ("A*sin(w*t)")^2 is half of the rectangle form by A*A and the period T. student cannot visualize this i feel.

That is exactly why the above applet was designed for.

Black curve is the square of the red curve . However, it is similar to Blue curve (when B=0), the only difference is there is an offset. And the offset (difference between black curve and blue curve is a constant) which is always half the maximum value of black curve(independent of or ).

Reply #4 on: September 15, 2010, 05:35:49 pm » posted from:SAO PAULO,SAO PAULO,BRAZIL

Find it using search by google. URL http://powerelectrical.blogspot.com/2007/02/ac-power.html The above graph shows the instantaneous and average power calculated from AC voltage and current with a lagging power factor (φ=45, cosφ=0.71). Average power is the real power and instantaneous power is the apparent power.

Reply #6 on: September 17, 2010, 04:09:36 pm » posted from:,,Taiwan

Quote

other student learning difficulty and suggestion for applet ? the other part is the area under the curve "A*sin(w*t)" to ("A*sin(w*t)")^2 is half of the rectangle form by A*A and the period T. student cannot visualize this i feel.

Let's calculate the average on both side. The average of should be the same as average of And the sum of the above two average is So the average of equal to

Progress is impossible without change; and those who cannot change their minds cannot change anything.
..."George Bernard Shaw(1865-1950, Irish dramatist, essayist and critic, Nobel Prize for Literature 1925)"