# Current Law and Flowrate

For any circuit, fluid or electric, which has multiple branches and parallel elements, the flowrate through any cross-section must be the same. This is sometimes called the principle of continuity.

 Water analogy to DC circuits Voltage law Current law
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# Voltage Law and Pressure

 Water analogy to DC circuits Voltage law Current law
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# Ohm's Law-Poiseuille's Law

Ohm's law for electric current flow and Poiseuille's law for the smooth flow of fluids are of the same form.

 Water analogy to DC circuits
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# Will the bird on the high voltage wire be shocked?

 Electric current flow is proportional to voltage difference according to Ohm's law, and both the bird's feet are at the same voltage. Since current flow is necessary for electric shock, the bird is quite safe unless it simultaneously touches another wire with a different voltage. Want a scary job? Maintenance on high voltage transmission lines is sometimes done with the voltage "live" by working from a platform on a helicopter, sitting on a metal platform! The helicopter must make sure it doesn't touch neighboring wires which are at a different voltage.
 Water analogy to DC circuits
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# Basic DC Circuit Relationships

 DC circuits can be completely analyzed with these four relationships. Ohm's law I = V/R Power relationship P = VI Voltage Law The net voltage change is equal to zero around any closed loop. (This is an application of the principle of conservation of energy.) Current Law The electric current in = electric current out of any junction. (Conservation of charge)
 Water analogy to DC circuits
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DC Circuits

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