The voltage of the power supply is constant. 48 volts. The resistor is a fixed and constant 100 ohms. The load is a fixed and constant 6 watts load.
But the current of the load will change depending on the voltage applied to the load. And any change in current causes a change of voltage applied to the load due to a change of voltage dropped across the resistor. The VDSL2 ethernet range extender uses 6 watts. It can be powered from 10 to 48 volts. This is a real world application, not just an academic exercise to tease everyone. I really thought I would have the solution knocked out in 3 minutes. Took about an hour. From: David Milholen Sent: Thursday, March 09, 2017 7:29 PM To: [email protected] Subject: Re: [AFMUG] Ohms law The idea would be to remove the power source entirely and find the thevenin resistance. So is the resistance changing or is the voltage? On 3/9/2017 7:29 PM, Chuck McCown wrote: But what is the Thevenin equivalent of a constant POWER component? � Read my reply to Bill, there is feedback.� The voltage drop of the resistor changes the current drawn by the load which changes the voltage drop of the resistor and so on.� � From: David Milholen Sent: Thursday, March 09, 2017 6:24 PM To: [email protected] Subject: Re: [AFMUG] Ohms law � This is straight out of my Dc circuit analysis book from college. https://www.allaboutcircuits.com/textbook/direct-current/chpt-10/thevenins-theorem/ I kinda thought my voltage was a bit off but the 100ohm is not a fixed value. I just used Watts/volts to get my current. W/V=I I then used the current to get the voltage drop across the loop I*R=V drop Its been a while for the thevenins therom but if i do a little study I think I could get it. � On 3/9/2017 5:28 PM, Chuck McCown wrote: But what is the formula? � From: Dave Sent: Thursday, March 09, 2017 4:20 PM To: [email protected] Subject: Re: [AFMUG] Ohms law � Current =.125A at load Voltage=35.5 at load If my current is correct then I should be on point. Otherwise I would use Thevenins Therom to get closer. On 03/09/2017 05:08 PM, Chuck McCown wrote: The questions are: What is the current and voltage on the load.� � From: Chuck McCown Sent: Thursday, March 09, 2017 4:05 PM To: [email protected] Subject: [AFMUG] Ohms law � Had a fun afternoon.� � Solve this.... and give the general formula... � 48 volt power supply 100 ohm wire resistance to the load. 6 watt load. � Took me some time.� Not trivial.� -- -- --
