ANSWERS TO QUESTIONS Q1. THROUGH Q43.
A1. To protect people and circuits from possible hazardous conditions.
A2. A direct short, excessive current, and excessive heat.
A3. A condition in which some point in the circuit where full system voltage is present
comes in contact with the ground or return side of the circuit.
A4. A condition that is not a direct short but in which circuit current increases beyond
the designed current carrying ability of the circuit.
A5. A condition in which the heat in or around the circuit increases to a higher than
A6. In series, so total current will be stopped when the device opens.
A7. Fuses and circuit breakers.
A8. circuit breaker fuse.
A10. A, C.
A11. Current, voltage, and time delay.
A12. The amount of current the fuse will allow without opening.
A13. The ability of the fuse to quickly extinguish the arc after the fuse element melts
and the maximum voltage that cannot jump across the gap of the fuse after the fuse opens.
A14. Delay, standard, and fast.
A15. Delay-Motors, solenoids, or transformers. Standard-Automobiles, lighting or
electrical power circuits. Fast-Delicate instruments or semiconductor devices.
A16. 125 volts or less, 1.5 amperes, delay
250 volts or less, 1/8 ampere standard
A17. 125 volts or less, 1/16 ampere
250 volts or less, .15 ampere
A19. Post-type fuseholder
A20. Center connector
A21. Visual inspection, indicators, and using a meter.
A22. Put it back in the circuit. A good fuse will have zero ohms of resistance.
A23. The ohmmeter causes more than 1/500 ampere through the fuse when you check the fuse,
thus it opens the fuse.
A24. Use a resistor in series with the fuse when you check it with the ohmmeter.
A25. Turn the power off and discharge the circuit before you remove fuses. Use a fuse
puller (an insulated tool) when you remove fuses front clip-type fuse holders. When you
check fuses with a voltmeter, be careful to avoid shocks and short circuits.
A26. Not acceptable-wrong style
Substitute #3-smaller current rating
Substitute #1-identical, except higher voltage rating
Not acceptable-lower voltage rating
Not acceptable-higher current rating
Substitute #2-Faster time delay rating
A27. Check for the proper type of replacement fuse and proper fit.
A28. Be sure the power is off in the circuit and the circuit is discharged before
replacing a fuse. Use an identical replacement fuse if possible. Remove any corrosion from
the fuseholders before replacing the fuses.
A29. Improper fuse, corrosion, improper fit, and open fuse.
A30. Frame, operating mechanism, arc extinguishers, terminal connectors, and trip element.
A31. Thermal, magnetic, and thermal-magnetic.
A32. The thermal trip element makes use of a bimetallic element that bends with an
increase in temperature or current. The bending causes the trip bar to be moved releasing
A33. A circuit breaker that will trip even if the operating mechanism is held ON.
A34. A circuit breaker that can be overridden if the operating mechanism is held ON.
A35. In current sensitive or nonemergency systems.
A36. In emergency or essential circuits.
A37. Instantaneous, short time delay, and long time delay.
A38. It is the use of time delay ratings to cause the circuit breaker closest to the
faulty circuit to trip. This isolates the faulty circuit without affecting other circuits.
A39. CB1-long time delay; CB2, CB3-short time delay; CB4 through CB10-instantaneous.
A40. The power requirements of the circuit and the physical space available.
A41. A push button or push-pull circuit breaker (small size, low power).
A42. Check the applicable technical manual, obtain the approval of the electrical or
engineering officer (for shipboard circuit breakers), remove power from the circuit
breaker, and tag the switch that supplies power to the circuit breaker.
A43. Check the operating mechanism for smooth operation, check the contacts for pitting,
check the terminals for tightness and corrosion, check the mounting hardware for tightness
and wear, check all components for wear, and check the entire circuit breaker for