MICHELIN ECT FINAL EXAM QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026
Continuous Current Rating - Answers The current that the fuse is intended to normally carry
indefinitely, considering load type, application, and code requirements.
Interrupting Rating - Answers The maximum short circuit current that a fuse can safely interrupt
without rupturing, as required by the National Electric Code.
Current Limiting - Answers Associated with short circuit conditions, a fuse is current limiting if it
operates quickly under short circuit conditions, limiting the peak short circuit current.
Selective Coordination - Answers The need to prevent facility blackouts by ensuring that only the
protective device nearest the faulted circuit opens, maintaining a specific ratio between upstream
and downstream continuous current ratings.
What is the formula for Xl? - Answers 2(pi)fl
Ohm's Law - Answers Current is directly proportional to voltage and inversely proportional to
resistance
Kirchoff's Series Law - Answers The sum of the voltages drops around a circuit loop must be equal to
the applied voltage
Power Formula - Answers V x I
Kirchoff's parallel law - Answers The sum of the currents entering a junction must equal the sum of
currents leaving the junction
How do inductive prox. switches work? - Answers The oscillator circuit generates an electromagnetic
field, when a metallic object approaches the sensor, it disrupts the electromagnetic field and induces
eddy current in the metal object. The sensor detects the change in emf and triggers the output.
Hysteresis - Answers Prevents chattering
How do capacitive prox. switches work? - Answers When an object comes close to the sensor it alters
the electric field between the two conductive plates, the change in the dielectric constant affects the
capacitance. An oscillator inside the switch detects the changing capacitance and triggers a signal.
Light mode - Answers Output is on whenever the receiver can see light from the light source.
Dark mode - Answers Output is on whenever the receiver cannot see light from the light source.
Photocell - Answers A sensor that uses light to detect the presence or absence of an object.
Transmitted Beam Photocell - Answers A photocell that has two parts, the emitter and receiver, in
two different housings opposite each other.
Retroreflective Photocell - Answers A photocell where the emitter and receiver are in the same
housing. A reflective material is placed where the photocell is facing.
Diffuse Photocell - Answers A sensing mode in which light strikes an object surface and is diffused
from the surface at all angles and detected by the sensor.
How do ultrasonic prox. switches work? - Answers Ultrasonic sensors work by emitting and receiving
high-frequency sound waves. Uses either oppose or diffuse mode.
Where are contactors found? - Answers In both the power and the control circuit.
What is the difference between a contactor and a relay? - Answers The contacts on a contactor are
rated for a higher voltage than the relay contacts.
How are eddy currents reduced in a contactor/relay? - Answers The stationary core is constructed of
laminated steel.
How are vibrations reduced in contactors/relays? - Answers Shading rings.
What is a CRM? - Answers Control relay master, a relay used to monitor all the safety devices and de-
energize if one opens.
What are the two basic types of overload relays? - Answers Thermal type and electronic current
monitoring type.
What are the three reasons an overload trips? - Answers Prolonged overcurrent (105% to 130% full
load current), phhase unbalance, and phase loss/single phasing.
Off delay timer - Answers Closes/opens the timed contacts instantly, then timer starts after the coil
gets de-energized. Has an arrow pointing down on the symbol.
On delay timer - Answers Closes/opens the timed contacts after the set time, then when the coil is
de-energized, the contacts go back to normal instantly. Has an arrow pointing up on the symbol.
What is an auxiliary block? - Answers An addon black that adds extra contacts to a relay or contactor.
What is capacitance? - Answers A capacitor can store electrical energy and also return this electricity
to the circuit. Capacitance is the property of a component which allows it to store electrical energy
, How does a solenoid work? - Answers A solenoid is an electrically controlled valve that operates a
mechanical valve.
What is peak voltage in AC? - Answers The maximum voltage, can be wrote as Vpeak or Vmax
What is the effective voltage called in AC? - Answers RMS voltage, or root mean square voltage
How is RMS voltage calculated? - Answers Vmax multiplied by .707
How is instantaneous current found? - Answers Ii = Imax x sin(phase angle)
How is frequency found? - Answers f = 1/t
How is time found? - Answers t = 1/f
What is the phase angle? - Answers How many degrees the voltage is leading the current by.
What type of load creates a phase angle? - Answers An inductive load.
What is inductance? - Answers Inductance opposes change in current flow, is measured in henrys(h)
and is represented by "L"
What creates inductance? - Answers A coil.
What is inductive reactance? - Answers The opposition to AC current due to the inductance. The unit
is the ohm and is represented by Xl
What is impedance? - Answers The total opposition to current flow, taking resistance and inductance
into account. Measured in ohms and represented by Z
How is the phase angle calculated? - Answers Inverse cosine of resistance(r) divided by impedance(Z)
What are the three types of power in a circuit with impedance? - Answers Preal, Qreactive, and
Sapparent
How is Preal found? - Answers Vt x It x cos(phase angle), measured in watts (W)
How is Qreactive found? - Answers Vt x It x sine(phase angle), measured in VARS
How is Sapparent found? - Answers Vt x It, measured in volt amperes (VA)
What is the power factor? - Answers The power factor is how efficiently power is being used, can be
expressed as a percent or as a decimal.
How is PF found? - Answers cos(phase angle)
What is a fuse? - Answers A protection device that prevents damage to the circuit in the case of
overcurrent.
What is a short circuit? - Answers A path of current not confined to normal conducting paths and is
several hundred times greater than normal current levels.
What is an overload? - Answers An overload is an excess of normal current but confined to normal
conducting paths.
What is the voltage rating of a fuse? - Answers The voltage rating is the maximum current voltage in
which the fuse can be safely applied.
Dual Element Fuses - Answers Fuses with two fusible elements (thermal cutout and fuse link)
connected in series, providing time delay on overloads and current limiting on short circuits.
Time Delay - Answers Delay in the fuse operation that allows motor starting current to be
disregarded as long as it is within five to six times the normal running current.
Overload Operation in Dual Element - Answers Operation where low overload current keeps the
short circuit fuse link inactive until the temperature of the center mass of copper reaches the melting
point of the solder, opening the circuit.
Thermal Cutout Element - Answers Component of dual element fuses with built-in time delay to
allow harmless surge currents like motor starting current to flow without opening the fuse.
Single Element Fuse - Answers Consists of a link or several links contained in a tube filled with arc-
quenching filler.
Overload Operation - Answers Occurs when an overload current higher than the rated current is
sustained for a sufficient time, causing the fuse link to melt. The resulting arc burns back the metal,
lengthening the gap until the circuit is interrupted.
Short Circuit Operation - Answers During a short circuit, multiple sections of the fuse links melt
instantly, leading to arcing across the vaporized parts. The arc-quenching filler aids in rapidly
extinguishing these arcs, clearing the circuit in a fraction of a second.
Current Limiting Fuses - Answers Fuses that have a total operating time of less than a half cycle (less
than 8/1000 of a second) during short circuit conditions, with even faster clearing times for high short
circuit currents, protecting system components from damage.
Continuous Current Rating - Answers The current that the fuse is intended to normally carry
indefinitely, considering load type, application, and code requirements.
Continuous Current Rating - Answers The current that the fuse is intended to normally carry
indefinitely, considering load type, application, and code requirements.
Interrupting Rating - Answers The maximum short circuit current that a fuse can safely interrupt
without rupturing, as required by the National Electric Code.
Current Limiting - Answers Associated with short circuit conditions, a fuse is current limiting if it
operates quickly under short circuit conditions, limiting the peak short circuit current.
Selective Coordination - Answers The need to prevent facility blackouts by ensuring that only the
protective device nearest the faulted circuit opens, maintaining a specific ratio between upstream
and downstream continuous current ratings.
What is the formula for Xl? - Answers 2(pi)fl
Ohm's Law - Answers Current is directly proportional to voltage and inversely proportional to
resistance
Kirchoff's Series Law - Answers The sum of the voltages drops around a circuit loop must be equal to
the applied voltage
Power Formula - Answers V x I
Kirchoff's parallel law - Answers The sum of the currents entering a junction must equal the sum of
currents leaving the junction
How do inductive prox. switches work? - Answers The oscillator circuit generates an electromagnetic
field, when a metallic object approaches the sensor, it disrupts the electromagnetic field and induces
eddy current in the metal object. The sensor detects the change in emf and triggers the output.
Hysteresis - Answers Prevents chattering
How do capacitive prox. switches work? - Answers When an object comes close to the sensor it alters
the electric field between the two conductive plates, the change in the dielectric constant affects the
capacitance. An oscillator inside the switch detects the changing capacitance and triggers a signal.
Light mode - Answers Output is on whenever the receiver can see light from the light source.
Dark mode - Answers Output is on whenever the receiver cannot see light from the light source.
Photocell - Answers A sensor that uses light to detect the presence or absence of an object.
Transmitted Beam Photocell - Answers A photocell that has two parts, the emitter and receiver, in
two different housings opposite each other.
Retroreflective Photocell - Answers A photocell where the emitter and receiver are in the same
housing. A reflective material is placed where the photocell is facing.
Diffuse Photocell - Answers A sensing mode in which light strikes an object surface and is diffused
from the surface at all angles and detected by the sensor.
How do ultrasonic prox. switches work? - Answers Ultrasonic sensors work by emitting and receiving
high-frequency sound waves. Uses either oppose or diffuse mode.
Where are contactors found? - Answers In both the power and the control circuit.
What is the difference between a contactor and a relay? - Answers The contacts on a contactor are
rated for a higher voltage than the relay contacts.
How are eddy currents reduced in a contactor/relay? - Answers The stationary core is constructed of
laminated steel.
How are vibrations reduced in contactors/relays? - Answers Shading rings.
What is a CRM? - Answers Control relay master, a relay used to monitor all the safety devices and de-
energize if one opens.
What are the two basic types of overload relays? - Answers Thermal type and electronic current
monitoring type.
What are the three reasons an overload trips? - Answers Prolonged overcurrent (105% to 130% full
load current), phhase unbalance, and phase loss/single phasing.
Off delay timer - Answers Closes/opens the timed contacts instantly, then timer starts after the coil
gets de-energized. Has an arrow pointing down on the symbol.
On delay timer - Answers Closes/opens the timed contacts after the set time, then when the coil is
de-energized, the contacts go back to normal instantly. Has an arrow pointing up on the symbol.
What is an auxiliary block? - Answers An addon black that adds extra contacts to a relay or contactor.
What is capacitance? - Answers A capacitor can store electrical energy and also return this electricity
to the circuit. Capacitance is the property of a component which allows it to store electrical energy
, How does a solenoid work? - Answers A solenoid is an electrically controlled valve that operates a
mechanical valve.
What is peak voltage in AC? - Answers The maximum voltage, can be wrote as Vpeak or Vmax
What is the effective voltage called in AC? - Answers RMS voltage, or root mean square voltage
How is RMS voltage calculated? - Answers Vmax multiplied by .707
How is instantaneous current found? - Answers Ii = Imax x sin(phase angle)
How is frequency found? - Answers f = 1/t
How is time found? - Answers t = 1/f
What is the phase angle? - Answers How many degrees the voltage is leading the current by.
What type of load creates a phase angle? - Answers An inductive load.
What is inductance? - Answers Inductance opposes change in current flow, is measured in henrys(h)
and is represented by "L"
What creates inductance? - Answers A coil.
What is inductive reactance? - Answers The opposition to AC current due to the inductance. The unit
is the ohm and is represented by Xl
What is impedance? - Answers The total opposition to current flow, taking resistance and inductance
into account. Measured in ohms and represented by Z
How is the phase angle calculated? - Answers Inverse cosine of resistance(r) divided by impedance(Z)
What are the three types of power in a circuit with impedance? - Answers Preal, Qreactive, and
Sapparent
How is Preal found? - Answers Vt x It x cos(phase angle), measured in watts (W)
How is Qreactive found? - Answers Vt x It x sine(phase angle), measured in VARS
How is Sapparent found? - Answers Vt x It, measured in volt amperes (VA)
What is the power factor? - Answers The power factor is how efficiently power is being used, can be
expressed as a percent or as a decimal.
How is PF found? - Answers cos(phase angle)
What is a fuse? - Answers A protection device that prevents damage to the circuit in the case of
overcurrent.
What is a short circuit? - Answers A path of current not confined to normal conducting paths and is
several hundred times greater than normal current levels.
What is an overload? - Answers An overload is an excess of normal current but confined to normal
conducting paths.
What is the voltage rating of a fuse? - Answers The voltage rating is the maximum current voltage in
which the fuse can be safely applied.
Dual Element Fuses - Answers Fuses with two fusible elements (thermal cutout and fuse link)
connected in series, providing time delay on overloads and current limiting on short circuits.
Time Delay - Answers Delay in the fuse operation that allows motor starting current to be
disregarded as long as it is within five to six times the normal running current.
Overload Operation in Dual Element - Answers Operation where low overload current keeps the
short circuit fuse link inactive until the temperature of the center mass of copper reaches the melting
point of the solder, opening the circuit.
Thermal Cutout Element - Answers Component of dual element fuses with built-in time delay to
allow harmless surge currents like motor starting current to flow without opening the fuse.
Single Element Fuse - Answers Consists of a link or several links contained in a tube filled with arc-
quenching filler.
Overload Operation - Answers Occurs when an overload current higher than the rated current is
sustained for a sufficient time, causing the fuse link to melt. The resulting arc burns back the metal,
lengthening the gap until the circuit is interrupted.
Short Circuit Operation - Answers During a short circuit, multiple sections of the fuse links melt
instantly, leading to arcing across the vaporized parts. The arc-quenching filler aids in rapidly
extinguishing these arcs, clearing the circuit in a fraction of a second.
Current Limiting Fuses - Answers Fuses that have a total operating time of less than a half cycle (less
than 8/1000 of a second) during short circuit conditions, with even faster clearing times for high short
circuit currents, protecting system components from damage.
Continuous Current Rating - Answers The current that the fuse is intended to normally carry
indefinitely, considering load type, application, and code requirements.
