ohms, then you must have 10 amperes of current across RV and RL. Remember that E = IR.

If the values of the resistance of RV and RL are equal, then 5 amperes of current will flow

through each resistance (RV and RL).

example, assume that the current through RL is now 4 amperes and that the total current

across Rs is 9 amperes. With this drop in current, the voltage drop across Rs is 18 volts.

Consequently, the output of the regulator has increased to 102 volts. At this time, the

regulating device (RV) decreases in resistance and 6 amperes of current flows through this

4 amperes across RL). Therefore, 20 volts is dropped across Rs causing the output to

decrease back to 100 volts. You should know by now that if the load resistance (RL)

increases, the regulating device (RV) decreases its resistance to compensate for the change.

If RL decreases, the opposite effect occurs and RV increases.

4-101. Now consider the circuit when a decrease in load resistance takes place. When RL

decreases, the current through RL subsequently increases to 6 amperes. This action causes a

total of 11 amperes to flow through Rs, which then drops 22 volts. As a result, the output is

98 volts. However, the regulating device (RV) senses this change and increases its

resistance so that less current (4 amperes) flows through RV. The total current again

becomes 10 amperes and the output is again 100 volts.

4-102. From these examples, you should know that the shunt regulator maintains the

desired output voltage by doing the following:

Sensing the current change in the parallel resistance of the circuit.

Compensating for the change.

4-103. Refer to Figure 4-33 to consider how the voltage regulator operates to compensate

for changes in input voltages. Remember that the input voltage may vary. Any variation

must be compensated for by the regulating device. If an increase in input voltage occurs,

the resistance of RV automatically decreases to maintain the correct voltage division

between RV and Rs. Therefore, notice that the regulator operates in the opposite way to

compensate for a decrease in input voltage.

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