Find The Internal Resistance Of A Power Supply

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Coursework To Find The Internal Resistance Of A Power Supply

The electrical supply on satellites needs to be kept at a constant voltage and the lost volts need to be taken into account when drawing different currents.

Aim

The aim of this investigation is to find the internal resistance of a power supply and to see if this value changes at five different voltage settings. Using a variable resistor to vary the load resistance at different voltage settings and obtaining both ampere and voltage readings and then plotting graphs of terminal potential difference against current to find the different values for the internal resistance of the power supply.

Theory

We can investigate the internal resistance of a power supply by setting up a circuit such as the one shown in figure 1. The voltmeter is connected in parallel to measure the potential difference across the power supply and the ammeter is connected in series to measure the flow of current.

We would connect the voltmeter across the terminals of the power supply. The variable resistor is used to vary the load resistance to gain a series of values for current and corresponding voltmeter readings.