Electrical Level 2 Module 10 Circuit Breakers and Fuses
Exam With Complete Solutions
Cartridge Fuse:
A fuse enclosed in an insulated tube to confine the arc when the fuse blows.
Circuit Breaker:
A device that is designed to open a circuit automatically at a certain over-current. It can
also be used to manually open and close the circuit.
Dual-element fuse:
A fuse having 2 fuse characteristics; the usual combination is an overcurrent limit and a
time delay before activation.
Edison-base:
The standard screw base used for ordinary lamps and Edison-base plug fuses.
Fault Current:
The current that exists when an unintended path is established between an ungrounded
conductor and ground.
Frame size:
A method used to classify circuit breakers according to given current ranges.
Fuse:
A protective device that opens a circuit when the fusible element is severed by heating
due to a fault current or overcurrent passing through it.
Fuse Link:
The fusible part of a cartridge fuse.
Molded-case circuit breaker:
A circuit breaker enclosed in an insulating housing.
Nonrenewable fuse:
A fuse that must be replaced after it interrupts a circuit.
Overcurrent protection:
, De-energizing a circuit whenever the circuit exceeds a pre-determined value; the usual
devices are fuses, circuit breakers, or magnetic relays.
Plug Fuse:
A type of fuse that is held in position by a screw thread contact instead of spring clips,
as is the case with a cartridge fuse.
Pole:
The portion of a device associated exclusively with one electrically separated
conducting path of the main circuit or device.
Short circuit:
The current that exists when an unintended path is created between any two
components in a circuit.
Overloads are most often between __ and __ times the normal current level.
1, 6
NEC Section 110.3(B)
Installation and Use: Listed or labeled equipment shall be used and installed in
accordance with any instructions included in the listing or labeling.
NEC Section 110.9
Interrupting Rating: Equipment intended to interrupt current at fault levels shall have an
interrupting rating at nominal circuit voltage at least equal to the current that is available
at the line terminals of the equipment. Equipment intended to interrupt current at other
than fault levels shall have an interrupting rating at nominal circuit voltage not less than
the current that must be interrupted.
NEC Section 240.83(C)
Interrupting Rating: Every circuit breaker having an interrupting rating other than 5,000A
shall have its interrupting rating shown on the circuit breaker.
NEC Section 240.83(E)
Voltage Marking: Circuit breakers shall be marked with a voltage rating that is not less
than the nominal system voltage that is indicative of their capability to interrupt fault
currents between phases or from phase to ground.
Where in the NEC would you find information on circuit breaker applications?
NEC Section 240.85
Exam With Complete Solutions
Cartridge Fuse:
A fuse enclosed in an insulated tube to confine the arc when the fuse blows.
Circuit Breaker:
A device that is designed to open a circuit automatically at a certain over-current. It can
also be used to manually open and close the circuit.
Dual-element fuse:
A fuse having 2 fuse characteristics; the usual combination is an overcurrent limit and a
time delay before activation.
Edison-base:
The standard screw base used for ordinary lamps and Edison-base plug fuses.
Fault Current:
The current that exists when an unintended path is established between an ungrounded
conductor and ground.
Frame size:
A method used to classify circuit breakers according to given current ranges.
Fuse:
A protective device that opens a circuit when the fusible element is severed by heating
due to a fault current or overcurrent passing through it.
Fuse Link:
The fusible part of a cartridge fuse.
Molded-case circuit breaker:
A circuit breaker enclosed in an insulating housing.
Nonrenewable fuse:
A fuse that must be replaced after it interrupts a circuit.
Overcurrent protection:
, De-energizing a circuit whenever the circuit exceeds a pre-determined value; the usual
devices are fuses, circuit breakers, or magnetic relays.
Plug Fuse:
A type of fuse that is held in position by a screw thread contact instead of spring clips,
as is the case with a cartridge fuse.
Pole:
The portion of a device associated exclusively with one electrically separated
conducting path of the main circuit or device.
Short circuit:
The current that exists when an unintended path is created between any two
components in a circuit.
Overloads are most often between __ and __ times the normal current level.
1, 6
NEC Section 110.3(B)
Installation and Use: Listed or labeled equipment shall be used and installed in
accordance with any instructions included in the listing or labeling.
NEC Section 110.9
Interrupting Rating: Equipment intended to interrupt current at fault levels shall have an
interrupting rating at nominal circuit voltage at least equal to the current that is available
at the line terminals of the equipment. Equipment intended to interrupt current at other
than fault levels shall have an interrupting rating at nominal circuit voltage not less than
the current that must be interrupted.
NEC Section 240.83(C)
Interrupting Rating: Every circuit breaker having an interrupting rating other than 5,000A
shall have its interrupting rating shown on the circuit breaker.
NEC Section 240.83(E)
Voltage Marking: Circuit breakers shall be marked with a voltage rating that is not less
than the nominal system voltage that is indicative of their capability to interrupt fault
currents between phases or from phase to ground.
Where in the NEC would you find information on circuit breaker applications?
NEC Section 240.85
