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Module 4 - Electronic Fundamentals B1 > 1.1a semiconductors > Flashcards

1.1a semiconductors Flashcards

1
Q

What gives the colour of an LED ?

A. The active element
B. The plastic it is encased in
C. The type of gas used inside it

A

A. The active element

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2
Q

A germanium diode is used for.
Option A. rectification.
Option B. voltage stabilization.
Option C. modulation.

A

A. Rectification

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3
Q
  1. Why is a diode put in parallel with an LED?.

Option A. To protect it from AC.
Option B. So it will work only above a certain voltage.
Option C. So it will work only below a certain voltage.

A

A. to protect it from AC

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4
Q
  1. When testing the forward bias of a diode with a multimeter.

Option A. the positive lead of the ohmmeter is placed on the anode.
Option B. it does not matter which terminal the positive lead of the ohmeter is placed.
Option C. the positive lead of the ohmmeter is placed on the cathode.

A

Option A. the positive lead of the ohmmeter is placed on the anode.

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5
Q

Which of the following describes the characteristics of a Thyristor?.

Option A. High voltage handling.
Option B. High power handling.
Option C. High current handling

A

Option C. High current handling

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6
Q

Light Emitting Diodes (LEDs).

Option A. emit light of only one wavelength dependent on type.
Option B. have very wide viewing angles.
Option C. are easily damaged if forward biased b more than 5V.

A

Option A. emit light of only one wavelength dependent on type

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7
Q

In a semiconductor junction diode, electrons are the minority carriers.

Option A. within the N region.
Option B. within the P region.
Option C. in both the N and P regions

A

Option B. within the P region

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8
Q

A silicon diode, when compared to a germanium diode has.

Option A. a higher forward bias voltage.
Option B. the same forward bias voltage.
Option C. less forward bias voltage.

A

Option A. a higher forward bias voltage.

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9
Q

This symbol is.

Option A. a transistor.
Option B. a diode.
Option C. a triac.

A

Option B. a diode

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10
Q

This symbol is.

Option A. a photodiode.
Option B. a laser diode.
Option C. an LED.

A

Option A. a photodiode.

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11
Q

A zener diode.

Option A. allows current to flow in one direction.
Option B. stabilizes voltage at a predetermined level.
Option C. acts like a switch.

A

B. stabilizes voltage at a predetermined level.

Explanation. Zener diodes are usually used in voltage regulator circuits.

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12
Q

A junction diode.

Option A. is similar to a vacuum diode but cannot rectify.
Option B. has one p-n junction.
Option C. can handle only very small currents

A

Option B. has one p-n junction.

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13
Q

Reverse bias.
Option A. greatly increases the majority carrier current.
Option B. lowers the potential barrier.
Option C. raises the potential barrier.

A

C. raises the potential barrier.

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14
Q

A diode connected across a relay coil is used to.

Option A. dissipate coil spikes on switch off.
Option B. allow the coil to energize with only one polarity.
Option C. cause a delay in switching on.

A

Option A. dissipate coil spikes on switch off.

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15
Q

To check the forward resistance of a diode with a multimeter, the lead connected to the positive terminal is put to the.

Option A. anode.
Option B. cathode.
Option C. either anode or cathode.

A

Correct Answer is A. anode.

Explanation. To forward bias a diode with a multimeter, the positive lead must be connected to the anode. Note: If it were a moving coil meter, you must connect the negative lead to the anode since the positive end of the battery is connected to the negative lead.

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16
Q

A thyristor has which of the following?.
Option A. A positive temperature coefficient.
Option B. High resistance when switched off.
Option C. High resistance when switched on.

A

Correct Answer is. C . High resistance when switched off.

Explanation. The thyristor (such as an SCR or TRIAC) is basically a switch which provides a high resistance when switched off.

17
Q

What does the circuit shown do?.
Option A. Full wave rectifier.
Option B. Half wave rectifier.
Option C. Voltage doubler.

A

Correct Answer is. Half wave rectifier.
Explanation. The diagram shows a half wave rectifier. The capacitor is for smoothing the output. A full wave rectifier requires 4 diodes and a voltage doubler requires two capacitors.

18
Q

In an LED, what is used to make the colour?.
Option A. The plastic lens cover.
Option B. The electrons.
Option C. The doping material.

A

Correct Answer is. The doping material.
Explanation. The dopant is what gives the LED its colour.

19
Q

An atom with 5 electrons in its outer shell is part of.
Option A. a C type material.
Option B. a P type material.
Option C. an N type material.

A

Correct Answer is. an N type material.

Explanation. An atom with five electrons in its outer shell (pentavalent) will provide an extra free electron and make the material an N type.

20
Q

A thyristor is commonly used for.
Option A. overvolts regulation.
Option B. voltage regulation.
Option C. rectification.

A

Correct Answer is. rectification.

Explanation. A thyristor (especially an SCR) is often used for rectification.

21
Q

A diode which emits photons when conducting is a.
Option A. light emitting.
Option B. varactor.
Option C. zener.

A

Correct Answer is. light emitting.

Explanation. Photons = light, so a diode which emits light is a Light Emitting Diode.

22
Q

The electrodes of an SCR are.

Option A. gate, cathode, anode.
Option B. source, drain, gate.
Option C. anode, cathode, source.

A

Correct Answer is. gate, cathode, anode.

Explanation. The electrodes of an SCR are the anode, cathode and the gate.

23
Q

Forward voltage of a silicon diode is.

Option A. 1.6V.
Option B. 0.6V.
Option C. 0.2V.

A

Correct Answer is. 0.6V.

Explanation. Si = 0.6V, Ge = 0.2V

24
Q

What is the typical volts drop across an LED.

Option A. 0.2V.
Option B. 0.4V.
Option C. 1.6V.

A

Correct Answer is. 1.6V.

Explanation. An LED volts drop is typically 1.6 - 2.4V.

25
Q

What diode gives off light photons when forward biased.
Option A. LED.
Option B. Gunn diode.
Option C. Schottky diode.

A

Correct Answer is. LED.
Explanation. LEDs give off light (photons) when forward biased.

26
Q

The anode of a diode is connected to a +4V DC supply and the cathode is connected to a +2V DC supply. The diode is.

Option A. forward biased not conducting.
Option B. reverse biased not conducting.
Option C. forward biased conducting.

A

Correct Answer is. forward biased conducting.

Explanation. Forward bias is anode to cathode. 4V fwd bias and 2V reverse bias, the diode is 2V fwd bias in total.

Module 4 - Electronic Fundamentals B1 (1 decks)

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