17.3 PRACTICE PROBLEMS

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(ans. c)

1. Write the mnemonic program for the Ladder Logic below.

(ans. XIC 100, XIC 101, OR, OTE 201)

2. A PLC can be used effectively to,

a) replace a few relays.

b) replace customized electronics.

c) replace a highly skilled human operator.

d) control a well understood process.

(ans. d)

5. Why would relays be used in place of PLCs?

(ans. for simple designs)

6. Give an example of where a PLC could be used.

(ans. to control a conveyor system)

7. Give a concise description of a PLC.

8. List the advantages of a PLC over relays.

9. Explain the trade-offs between relays and PLCs for control applications.

10. In the figure below, if a limit switch is NO, the power the power flow to the output will normally be___________________.

(ans. off)

11. In the figure above, if a limit switch input is NC, the power indicator in the input module should be __________________.

(ans. on)

12. TRUE or FALSE - The left-most side of the PLC's ladder diagram simulates the power line.

(ans. true)

13. In ladder diagram programs, all outputs are represented by:

a) Contact symbols

b) Coil symbols

c) a or b

d) None of the above

(ans. b)

14. List the advantages of PLCs over relay logic.

15.