Enter your circuit's Thevenin Voltage (Vth) and Thevenin Resistance (Rth), then set a Load Resistance (RL) to see the Power Delivered to Load, alongside the Maximum Possible Power, Optimal Load Resistance, Transfer Efficiency, and Load Current — so you know exactly how close your circuit is to peak performance.
Power Delivered to Load
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Maximum Possible Power
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Optimal Load Resistance
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Transfer Efficiency
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Load Current
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The Maximum Power Transfer Theorem states that maximum power is delivered from a source to a load when the load resistance equals the source resistance (Thevenin resistance). At this condition, the efficiency is 50%.
Maximum power transfer is calculated using the formula: P = (Vth²×RL)/(RL+Rth)². The maximum occurs when RL = Rth, giving Pmax = Vth²/(4×Rth).
The theorem applies only to linear circuits with resistive loads. It assumes the source resistance is fixed and doesn't consider efficiency, which is only 50% at maximum power transfer conditions.
At maximum power transfer (RL = Rth), half the power is dissipated in the source resistance and half in the load resistance, resulting in 50% efficiency. Higher efficiency requires RL >> Rth.
Maximum power transfer is crucial in applications like audio amplifiers, antenna systems, and signal processing where extracting maximum power from the source is more important than efficiency.
A Thevenin equivalent circuit represents any linear circuit as a voltage source (Vth) in series with a resistance (Rth). This simplification makes it easier to analyze power transfer to different loads.
Power delivery depends on the ratio of load to source resistance. Power increases as RL approaches Rth, peaks when RL = Rth, then decreases as RL continues to increase.