Silicon Controlled Rectifiers Quiz
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Questions and Answers

What is one of the primary advantages of using a Silicon Controlled Rectifier (SCR) over traditional diodes?

  • SCRs can operate at lower voltages.
  • SCRs can control high power applications. (correct)
  • SCRs allow current in both directions.
  • SCRs are easier to manufacture than standard diodes.

    • Which of the following best describes the composition of a Silicon Controlled Rectifier?

  • Two layers of semiconductor material.
  • A single layer of silicon material.
  • Four layers of alternating P-type and N-type materials. (correct)
  • Three terminal and five layer semiconductor.

    • After its initial development, what alternative names were often used for the Silicon Controlled Rectifier?

  • Thyristor and controlled rectifier. (correct)
  • Diode and SCR diode.
  • Transistor and BJT.
  • FET and direct current converter.

    • Which of the following applications is NOT typically associated with Silicon Controlled Rectifiers?

    <p>Light bulbs.</p> Signup and view all the answers

    What principle is the operation of a Silicon Controlled Rectifier based on?

    <p>p-n-p-n switching.</p> Signup and view all the answers

    Which phenomenon occurs when the forward bias voltage exceeds the breakdown voltage in an SCR?

    <p>Depletion region breakdown</p> Signup and view all the answers

    What is the role of the gate in a TRIAC?

    <p>To control the turn-on conditions</p> Signup and view all the answers

    In which region of the V-I characteristics does the SCR experience forward leakage current?

    <p>Forward blocking region</p> Signup and view all the answers

    What is the primary risk associated with exceeding the reverse breakdown voltage in an SCR?

    <p>Avalanche breakdown leading to damage</p> Signup and view all the answers

    What characteristic curve mode represents the first quadrant operation for a TRIAC?

    <p>Mode 1</p> Signup and view all the answers

    What occurs at junction J2 during Forward Blocking Mode?

    <p>Junction J2 does not allow current to flow.</p> Signup and view all the answers

    Which operation mode of the SCR occurs when both the anode is positively charged and the gate terminal receives a positive voltage?

    <p>Forward Conducting Mode</p> Signup and view all the answers

    What is the primary factor that allows current to flow in Forward Conducting Mode?

    <p>High energy minority carriers generated by collisions.</p> Signup and view all the answers

    What characteristic of the SCR remains during Reverse Blocking Mode?

    <p>A small leakage current may still be present.</p> Signup and view all the answers

    What effect does applying a positive voltage to the gate terminal have in Forward Conducting Mode?

    <p>It allows for lower voltage across the anode and cathode to trigger conduction.</p> Signup and view all the answers

    What characterizes Mode 2 operation in a TRIAC?

    <p>VMT21 is positive and VG1 is negative.</p> Signup and view all the answers

    Which of the following statements about DIAC is true?

    <p>It must exceed its break over voltage to conduct.</p> Signup and view all the answers

    What effect does the resistor R2 have in the TRIAC control circuit?

    <p>It controls the point of beginning of conduction.</p> Signup and view all the answers

    Which of the following is a disadvantage of using TRIACs?

    <p>They are less reliable compared to SCRs.</p> Signup and view all the answers

    What happens to a DIAC when the voltage falls below its holding current?

    <p>It switches to the off-state.</p> Signup and view all the answers

    What is the purpose of adding external resistance in triac operations?

    <p>To limit excess current during conduction.</p> Signup and view all the answers

    What is the relationship between the break over voltage and the symmetrical properties of a DIAC?

    <p>The break over voltage is equal for both forward and reverse polarities.</p> Signup and view all the answers

    Which triggering method utilizes light to turn on an SCR?

    <p>Light Triggering</p> Signup and view all the answers

    What occurs during forward voltage triggering just before the SCR turns ON?

    <p>Avalanche breakdown occurs at junction J2</p> Signup and view all the answers

    What is a key drawback of temperature triggering in SCR operation?

    <p>It can lead to thermal runaway and device damage</p> Signup and view all the answers

    What characteristic makes DIAC advantageous in reducing harmonics within a system?

    <p>Symmetrical switching characteristics</p> Signup and view all the answers

    In dV/dt triggering, what phenomenon allows the SCR to turn ON?

    <p>High rate of rise of voltage causing a transient gate current</p> Signup and view all the answers

    Which of the following best describes the primary limitation of a DIAC?

    <p>Conducts only above 30 volts</p> Signup and view all the answers

    What is a notable disadvantage of gate triggering using a DC supply?

    <p>It causes more losses in the gate circuit</p> Signup and view all the answers

    Which of the following best describes forward blocking mode in SCR operation?

    <p>Junctions J1 and J3 are forward biased and J2 is reverse biased</p> Signup and view all the answers

    In the two transistor analogy of SCR, which condition must be satisfied for the transistors to enter saturation?

    <p>Transistor 2 is in cutoff mode with zero base current</p> Signup and view all the answers

    What happens during the latch-up phase of an SCR's turn-on mechanism?

    <p>The current reinforces the trigger effect</p> Signup and view all the answers

    Which mode of SCR operation should be avoided to prevent damage?

    <p>Forward blocking mode</p> Signup and view all the answers

    What is the significance of symmetrical triggering in TRIACs when using a DIAC?

    <p>Ensures equal voltage levels for both AC cycles</p> Signup and view all the answers

    What condition leads to the conduction of the SCR in gate triggering?

    <p>Positive voltage applied at the gate while anode is positive</p> Signup and view all the answers

    Which of the following statements about SCR triggering methods is incorrect?

    <p>Gate-voltage triggering can apply non-threshold voltage.</p> Signup and view all the answers

    Which of the following statements about the SCR's reverse blocking mode is true?

    <p>Junction J2 is forward biased and J1, J3 are reverse biased</p> Signup and view all the answers

    Which of the following is NOT a typical application of a DIAC?

    <p>Voltage regulation in high power circuits</p> Signup and view all the answers

    What does the holding current represent in the context of an SCR?

    <p>Minimum current needed to maintain conduction</p> Signup and view all the answers

    In SCR theory, which equation represents the relationship of anode current and gate current when leakage currents are negligible?

    <p>$I_a = [α_2 I_g] / [1 - (α_1 + α_2)]$</p> Signup and view all the answers

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