draws more and more current until the voltage drop across Rs reduces the output to the zener voltage at the current value needed, which is still just about 12 volts. At no load the zener is drawing the full 0.5a needed to hold the voltage at 12 volts. Thus, no matter what the load, within the design limits, the voltage will remain at twelve volts. However, the zener regulates by turning power into heat. With twelve volts across it, and 0,5a of current passing through it, 1 he zener is dissipating 6 watts. A ten watt zener can safely dissipate this power if mounted on a good heat sink (not just a chassis!!). Notice that the zener can also regulate a varying input. The input can rise to any value, and the zener will still regulate. However care must be taken that the power dissipated does not exceed the ratings. The input voltage can drop
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