How Does Current Behave Over Time in AC Circuits?

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In AC circuits, the relationship between current and voltage can be complex, particularly in purely resistive loads where current and voltage are in phase. While voltage fluctuates, current also varies accordingly, contradicting the notion that current remains constant. When measuring fluctuating voltage, it is essential to measure the corresponding fluctuating current. For average measurements, using root mean square (RMS) values for both voltage and current is necessary, but multiplying these RMS values does not always yield accurate power calculations due to the influence of the power factor. Understanding these dynamics is crucial for effective power engineering.
Benjamin_harsh
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Homework Statement
Current Vs Time in AC Current.
Relevant Equations
Current Vs Time in AC Current.
I always find voltage vs time majorly in case of AC current. What about current V time in AC current cases?
 
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One can plot current versus time, certainly.

For a purely resistive load (an AC power source driving current through a resistor), how does current relate to voltage?
 
jbriggs444 said:
One can plot current versus time, certainly.

For a purely resistive load (an AC power source driving current through a resistor), how does current relate to voltage?
So how current stays same while voltage repeatedly fluctuates in AC current?
 
Benjamin_harsh said:
So how current stays same while voltage repeatedly fluctuates in AC current?
Current does not stay the same in this situation.

If you are measuring a fluctuating voltage, you should be working to measure a fluctuating current.

If you are measuring an average (for instance, a root mean square average) voltage then you should be working to measure an average (for instance, a root mean square average) current.

Note that multiplying RMS voltage by RMS current is not guaranteed to yield RMS power. Hence the notion of a power factor. [That was a serious learning moment when I first encountered that -- those power engineering dudes face interesting challenges. Some of them hang out here]
 
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Thread 'Chain falling out of a horizontal tube onto a table'

Thread 'Chain falling out of a horizontal tube onto a table'

My attempt: Initial total M.E = PE of hanging part + PE of part of chain in the tube. I've considered the table as to be at zero of PE. PE of hanging part = ##\frac{1}{2} \frac{m}{l}gh^{2}##. PE of part in the tube = ##\frac{m}{l}(l - h)gh##. Final ME = ##\frac{1}{2}\frac{m}{l}gh^{2}## + ##\frac{1}{2}\frac{m}{l}hv^{2}##. Since Initial ME = Final ME. Therefore, ##\frac{1}{2}\frac{m}{l}hv^{2}## = ##\frac{m}{l}(l-h)gh##. Solving this gives: ## v = \sqrt{2g(l-h)}##. But the answer in the book...
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