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Zorluk: OrtaProtective Devices

An electronics technician is servicing power supplies and control circuits containing various protection components. Match each circuit protective device or mechanism on the left with its primary operational principle on the right.

  • Magnetic trip mechanism in a circuit breakerUtilizes electromagnetic flux from severe overcurrent surges to instantaneously pull an armature and open contacts
  • Bimetallic strip in a thermal circuit breakerBends progressively due to unequal thermal expansion from prolonged current heating until it releases a mechanical latch
  • Polymeric positive temperature coefficient (PPTC) resettable fuseTransitions from low to high electrical resistance when internal I2RI^2R heating disrupts conductive polymer chains, resetting after cooling
  • Transient voltage suppression (TVS) diodeConducts heavily via avalanche breakdown across power rails when voltage exceeds a breakdown rating to clamp fast voltage spikes

Cevap

Magnetic trip mechanism matches with electromagnetic flux pulling an armature for instantaneous tripping; Bimetallic strip matches with progressive bending from thermal expansion during prolonged overcurrents; PPTC resettable fuse matches with transitioning to high resistance upon I2RI^2R heating and self-resetting; TVS diode matches with avalanche breakdown to clamp fast transient overvoltage spikes.
Each protective device is correctly paired with its operating physics: magnetic elements react instantly to short circuits via electromagnetic attraction; bimetallic strips bend slowly in response to resistive heat during continuous overloads; PPTC devices restrict current by increasing resistance when heated and recover when cool; and TVS diodes suppress voltage spikes through fast avalanche breakdown in parallel with the load.

Adım Adım Çözüm

1
Distinguish between overcurrent protective devices and transient overvoltage suppression devices.
Identify that circuit breaker elements and PPTC fuses protect against excessive current flow, whereas TVS diodes protect against voltage transients.
Protective devices function either as series current limiters/interrupts or parallel voltage clamps.
2
Differentiate between the dual trip mechanisms of thermal-magnetic circuit breakers.
The magnetic solenoid provides instantaneous response to large short-circuit currents, while the bimetal strip provides an inverse-time response to moderate sustained overloads.
Magnetic tripping prevents catastrophic equipment damage during direct shorts, whereas thermal tripping prevents wire insulation overheating from prolonged overloads.
3
Examine the solid-state behavior of PPTC fuses and TVS diodes.
PPTC devices rely on temperature-dependent polymer resistance expansion to limit overcurrent, while TVS diodes rely on p-n junction avalanche breakdown to shunt transient overvoltage.
Associating each solid-state component with its physical trigger establishes the correct pairs.

Anahtar Kavram

Operational Principles of Overcurrent and Overvoltage Protective Devices
Tahmini Süre:1m 15s
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Protective Devices

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