Examkin

Soru

Zorluk: ZorIgnition System

An automotive technician connects an oscilloscope to an inductive ignition coil and observes that the high-voltage firing spike occurs at the precise moment primary circuit current is interrupted by the switching module. Which of the following electrical processes causes the ignition coil to generate this high-voltage output needed to bridge the spark plug gap?

  1. A
    The continuous DC charging output from the alternator surges directly into the secondary windings when engine speed increases.
  2. The rapid collapse of the magnetic field in the primary winding cuts across the secondary winding, inducing a high-voltage surge.Cevap
  3. C
    The mechanical pressure generated during the piston compression stroke builds an electrostatic charge that discharges across the coil windings.
  4. D
    A rich air-fuel mixture inside the combustion chamber pre-ionizes the spark plug gap, drawing excess secondary voltage from the battery.

Cevap

The rapid collapse of the magnetic field in the primary winding cuts across the secondary winding, inducing a high-voltage surge.
An automotive ignition coil functions as a step-up pulse transformer. When the ignition module opens the primary circuit, current flow stops immediately. This causes the magnetic field created by the primary winding to collapse abruptly across the secondary winding. Because the secondary winding contains far more turns of finer wire than the primary winding, this rapid collapse induces a high-voltage spike (20,000 to 50,000+ volts) capable of arcing across the spark plug gap.

Adım Adım Çözüm

1
Analyze primary circuit operation during dwell time.
Low-voltage current (12V) flows through the heavy primary winding turns, building a strong electromagnetic field around the soft iron core.
Current through an inductor stores energy in the form of a magnetic field.
2
Evaluate the switching event when the primary circuit is opened.
The primary circuit ground is interrupted, causing current flow to cease and the magnetic field to collapse almost instantaneously.
Removing current removes the magnetic field support, initiating rapid field decay.
3
Apply Faraday's law of mutual induction across the step-up windings.
The rapidly decaying magnetic field lines cut across the secondary winding's high number of turns, generating 20,000 to 50,000 volts.
Induced voltage is proportional to the rate of magnetic flux change and the ratio of secondary-to-primary turns.

Anahtar Kavram

Mutual electromagnetic induction and magnetic field collapse in step-up ignition coils
Tahmini Süre:1m 30s
Bu soruyu puanla

Konular

Ignition System

Bu konudan daha fazla soru