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Getting my head around resistance

Discussion in 'General Electronics Discussion' started by Ringojames, Jul 5, 2012.

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  1. Ringojames


    Jul 5, 2012
    Hi guys

    I'm new to the forum and would like a bit of help regarding resistance I'm studying for my MESF (don't worry it's not a homework question) and I'm just covering resistance, the study question and answer are as follows

    An amplifier draws 50amps with an applied voltage of 12V, for full power output with both channels driven into a 4ohm load.

    What is the effective resistance of the amplifier ? Well the answer is 0.24 ohms!!

    My question is really, (without sounding thick) what does that tell us? Is 0.24 ohms ok or not ok? What would happen if the answer was more than 4 ohms what could be done if it was etc.

    Thank you for your time
  2. john monks

    john monks

    Mar 9, 2012
    The question is essentially, what is the resistance of a circuit that has 12 volts across it and draws 50 amps. This is just an ohms law question. Naturally if you Increase the speaker resistance the power supply would see more resistance but the question was not about that. To me this seems like a trick question but I suspect the course is full of irrelevant data being added to the problem just to add confusion. Physics courses are even worse for this. The important thing is that you keep in mind is the science and definitions. Remember that by definition that resistance is equal to the voltage divided by the current and that scientific evidence shows us that current is directly related to the voltage divided by the resistance.

    CDRIVE Hauling 10' pipe on a Trek Shift3

    May 8, 2012
    Like John I'm not sure what you're asking either but I suspect you might be asking about power transfer as it applies to load & source resistance or impedance. Take a look at the attachment and let us know if this is what your questioning. Note that I used the term "Impedance" because 'Maximum Power Theorem' applies to AC or DC circuits. In this example 'Resistance' is equivalent to 'Impedance'. The plot displays Wattmeter readings of a load (RL) that is varied from zero to 8 Ohms. The voltage source (VG1) is held constant at 10VDC. The internal impedance of VG1 = 4 Ohms.

    Attached Files:

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