In the illustrated motor controller, the...

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Question 1 of 2066636eed28f7522a1c51d691

In the illustrated motor controller, the motor fails to start. A voltmeter reading between 1 and 5 reads line voltage, while the voltmeter reading between 2 and 5 reads 0 VAC. What is most likely the problem? Illustration EL-0007

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Question 1 of 20

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🔍 Key Concepts

• Trace the control circuit from L1 through the Stop and Start switches to the M coil and OL contact using the lower (B) diagram. • Think about what a 0 VAC reading between two test points really means about their electrical connection and potential. • Compare how an open Stop, open Start, open M coil, or open OL contact would change the voltage readings between points 1–5 and 2–5.

💭 Think About

• If there is full line voltage between 1 and 5, which points in the circuit must still be correctly connected to the power lines? • For the reading between 2 and 5 to be 0 VAC, what must be true about the relationship between points 2 and 5: are they at the same potential, or is one of them completely floating with no source? • For each choice (A–D), imagine that specific component is open and mentally recalculate: what voltage would you expect between 1–5 and 2–5 in that scenario?

✅ Before You Answer

• Verify which line each numbered test point (1,2,3,4,5) connects to when the Start is pressed and components are normal. • For each possible open component, check whether point 2 would still be tied to L1 or instead end up connected only through the M coil and OL contact to point 5. • Before choosing, be sure your option makes 1–5 show line voltage AND 2–5 show 0 VAC at the same time; eliminate any choice that fails either condition.

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