# Finding appropriate source for the electrical load

Have four circuits. One takes 9Vdc, two 5Vdc, and last one takes 12Vdc. Have variable transformer for source. How do I calculate or choose the voltage needed to run all four circuits with out blowing them all up, and at the same time run each circuit by themselves or two at a time or three, etc. How do I know how much current the source needs and where do I place leads to measure current and voltage for each individual circuit?

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#### Solution Preview

Find the resistance of each of the loads by connecting a multimeter to the leads of the eqipment. Now find V/R for each device, which gives the value of the current each of them needs.

To run all the circuits at the same time, the source must be able to ...

#### Solution Summary

Solution with all explanations and mathematical steps. The appropriate source for the electrical loads are given. The voltages are analyzed.