Question 7.20: Suppose that you measure 24 V with the voltmeter in Figure 7...

Step 1: Analysis
There is no voltage drop across R_{1} because both sides of the resistor are at +24 V. Either there is no current through R_{1} from the source, which tells you that R_{2} is open in the circuit, or R_{1} is shorted.

Step 2: Planning
The most probable failure is an open R_{2}. If it is open, then there will be no current from the source. To verify this, measure across R_{2} with the voltmeter. If R_{2} is open, the meter will indicate 24 V. The right side of R_{2} will be at zero volts because there is no current through any of the other resistors to cause a voltage drop across them.

Step 3: Measurement
The measurement to verify that R_{2} is open is shown in Figure 7-53