Mechatronics Questions and Answers – Solid State Electronic Devices – DIAC

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This set of Mechatronics Multiple Choice Questions & Answers (MCQs) focuses on “Solid State Electronic Devices – DIAC”.

1. How many minimum thyristors are required to make a TRIAC (Triode alternating current)?
a) 0
b) 1
c) 2
d) 3
View Answer

Answer: c
Explanation: 2 thyristors are required to make a TRIAC (Triode alternating current). These thyristors are connected parallel to each other but in opposite direction. Their gates are made common, which makes it a 3 terminal device.
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2. How many terminals does a DIAC (Diode alternating current) have?
a) 1
b) 2
c) 3
d) 4
View Answer

Answer: b
Explanation: DIAC (Diode alternating current) is a 2 terminal device. It has got two zener diodes connected back to back which forms a DIAC (Diode alternating current). The two terminals are anode terminals in a PNPN DIAC (Diode alternating current).

3. What are present at the potential barrier of a PN junction when no external voltage is applied?
a) Electrons
b) Holes
c) Positive Ions
d) Positive and Negative Ions
View Answer

Answer: d
Explanation: Positive and Negative Ions are present at the potential barrier of a PN junction when no external voltage is applied. These Ions are immobile and are accumulated which does not allow the electrons and holes to cross the junction until an external voltage is applied.
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4. Which is an example of DIAC?
a) OptoNCDT ILR 1030
b) OptoNCDT1420
c) NTE6408
d) EddyNCDT 3301
View Answer

Answer: c
Explanation: NTE6408 is an example of DIAC. OptoNCDT ILR 1030 and OptoNCDT1420 are laser sensor used for computing distance and objects placed at very high distances. EddyNCDT 3301 is a Eddy currents sensor.

5. DIAC is a unidirectional device.
a) True
b) False
View Answer

Answer: b
Explanation: DIAC (Diode alternating current) is a not a unidirectional device, it is a bidirectional device. It is a thyristor that can be switched on in both polarities. It is mainly used in activating TRIAC (Triode alternating current).
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6. DIAC can act as AC switch.
a) True
b) False
View Answer

Answer: a
Explanation: DIAC can act as AC switch. It is one of the major application of DIAC (Diode alternating current). It is also extensively used to assist the triggering action of TRIAC (Triode alternating current) when used as a switch.

7. What is the breakdown voltage of three layered DIAC (Diode alternating current)?
a) Approximately 30 volts
b) Approximately 20 volts
c) Approximately 50 volts
d) Approximately 40 volts
View Answer

Answer: a
Explanation: 0.7 volts is the minimum voltage required to make the PN junction of a real silicon transistor in forward biased. This 0.7 volt potential difference makes the PN junction between base and emitter terminal in forward biased.
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8. How many layers of semiconductor does a DIAC have?
a) 1
b) 2
c) 3
d) 4
View Answer

Answer: d
Explanation: A DIAC (Diode alternating current)is a 4 layered semiconductor device. It has alternating P-type and N-type semiconductor fused together. Together these 4 layers form up a DIAC (Diode alternating current).

9. What is the full form of SIDAC?
a) Silicon diode for alternating current
b) Silicate diode for alternating current
c) Silicon dioxide for alternating current
d) Silicon diode for analogous current
View Answer

Answer: a
Explanation: SIDAC stands for Silicon diode alternating current. It is a member of thyristor family that has 5 layers of n-type and p-type semiconductor layers fused together. They are used for switchimg and triggering pupose.
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10. A SIDAC (Silicon diode for alternating current) does not conduct below a break-over voltage.
a) True
b) False
View Answer

Answer: a
Explanation: A SIDAC (Silicon diode for alternating current) does not conduct below a break-over voltage. There is some specified voltage which has to be crossed by the input voltage, in order to make the SIDAC work. Further it does not depend on voltage.

11. DIAC starts to conduct current after some threshold voltage.
a) True
b) False
View Answer

Answer: a
Explanation: DIAC starts to conduct current after some threshold voltage. It starts to conduct current only when the input voltage crosses the breakdown voltage. It is also extensively used to assist the triggering action of TRIAC (Triode alternating current) when used as a switch.

12. DIAC’s get damaged when voltage of wrong polarity is applied at its terminals.
a) True
b) False
View Answer

Answer: b
Explanation: DIAC’s does get damage when voltage of wrong polarity is applied at the terminals. They are bidirectional device, that is they do not have fixed anode and cathode terminals. They work the same even if the polarity is changed.

13. What is the full form of DIAC?
a) Diode for alternating current
b) Diode attenuating current
c) Dioxide for analogous current
d) Diode analogous current
View Answer

Answer: a
Explanation: DIAC stands for Diode for alternating current. It only conducts current when the applied voltage crosses breakdown voltage. DIAC is a 2 terminal device. It has got two zener diodes connected back to back which forms a DIAC.

14. What is the full form of TRIAC?
a) Triode attenuating current
b) Triode for alternating current
c) Trioxide for analogous current
d) Triode analogous current
View Answer

Answer: b
Explanation: TRIAC stands for Triode for alternating current. 2 thyristors are required to make a TRIAC. It is a three terminal device. The thyristors are connected parallel to each other but in opposite direction and their gates are made common.

15. DIAC’s do not work with DC voltage.
a) True
b) False
View Answer

Answer: b
Explanation: DIAC’s do work with DC voltage. But it shows different behaviours with the DC voltage. IT works exactly same as the Shockley’s diode. A Shockley diode is a four layered, unidirectional diode composed of alternating N type and P type material.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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