in an a.c circuit with an load....the voltage across the load is constantly varying as a sine or cosine function....the current is also varying...in that case the power across the load is also varying...
this should obviously reflect in the change of intensity of the functioning of the load...which does not happen..
plz, explain the reason...
2006-11-21 04:36:52 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Physics
power=VI ,even though the voltage and current are variables,the total power for a fixed circuit with constant resistances,power is also constant .it is not variable.
we know ohm's law i.e V=IR,and this law is valid at constant resistance only.so,at constant resistance V is proportional to current.as constant resistance is maintained through out the operation of the circuit ,power is constant.and if both voltage and current are varied,power also varies.and this is the main reason for getting low and high voltages.
and we are getting constant results during our power supply or in experiments bcoz we are maintaining constant resistances.
I hope u understood the reason.thanq for innovative doubt.
2006-11-21 15:37:30 · answer #1 · answered by praveenplp 2 · 0⤊ 0⤋
A.C currents are used because they are easier to transmit across the power grid than D.C current. A device called a Rectifier converts the a.c into d.c for your equipment's use (computer, t.v etc). No, power does not vary, neither does current (the general direction of current flow is consistent). Voltage on the other hand may vary, hence the 110v-140v range indicator on most appliances (not sure about the range don't quote me).
2006-11-21 12:54:47 · answer #2 · answered by Anonymous · 0⤊ 0⤋
It happens and we can experience it also some time, but the fact remains. Sensitive equipment can even record it.
Simplest is high speed film taken of any event, when played back at very slow speed will make it clear that it is true.
In India you are using 50 Hz, in USA they went to 60 Hz long time ago.
Our eyes on an average retains an immage on retina for 1/16 of a second. If you are not an average person you may notice the fluctuations. To avoid the jucky motions in the movies the industry standard is lot higher speed then 16 frames per second at the inseption of movie camera.
2006-11-21 13:51:54 · answer #3 · answered by minootoo 7 · 0⤊ 0⤋
A/C circuits are inductive,capacitive or both.
Harmonics in an a/c circuit are the most detrimental.to the efficiency.
By balancing induction and capacitance a compromise produces the most efficient cct.
voltage and current vary continuously in a reactive cct.
Remember ELI and ICE.
In an inductive cct voltage leads current,
In a capacitive cct current leads voltage.
2006-11-21 13:31:07 · answer #4 · answered by Billy Butthead 7 · 0⤊ 0⤋
as the voltage across the load varies current varies in inverse proportion and in that way hewlps to keep the power same coz p=v*i*t, where p=power,i=current.v=voltage across the load .
2006-11-21 12:48:47 · answer #5 · answered by ANIRBAN B 2 · 0⤊ 0⤋
I disagree with your statement "which does not happen.." It does happen. Not in all cases, but in simple cases it does.
Incandescent light bulbs perhaps don't show it because the filament stays hot between peaks in the voltage and current. In a room lit with flourescent bulbs, if you watch the blades of a fan you can sometimes see that the rapid on/off/of/off of the light captures the fan blade so it appears to be moving slowly. LEDs also do this. It's just too quick to see easily.
2006-11-21 13:12:07 · answer #6 · answered by sojsail 7 · 0⤊ 0⤋