A supplied access-control voltage model

A classroom exercise models a compatible direct-current door-control component on an isolated training board. The supplied source voltage is 24 volts, load current is 0.5 ampere and total path resistance is 4 ohms. For this exercise only, the component information states an acceptable terminal range of 20 to 26 volts. A trainee compares the nominal source voltage with the range and ignores the path resistance. Another proposes replacing the entire access-control design on the basis of one arithmetic result. No real building connection, conductor installation method, fire-door approval or power-loss sequence is supplied. Students must calculate the modeled terminal voltage and explain what the calculation does and does not establish about the component and the complete door arrangement.