Download C. a pn junction. - E

TU: PN junction Subject: Physics
Class: 5 C - 20 students aged 18/19 Language level : B1 / B2
Teacher: Laurena Petrizzi
STEP 1. a. INTRODUCTION AND MOTIVATION
Electronics is very, very useful in a lot of applications.
Think, for example, about the reception of a signal and its further processing like the decoding of the speed of a motorbike: a high-speed
microprocessor inside a little box uses a digital software to encode the electrical pulse from the vehicle speed sensor.
A physical quantity like a sound, a picture, pressure, temperature is usually converted, by a transducer, into an electrical signal that can be
amplified, transmitted and received.
That is what happens for example in a sound transmission.
Nowadays most signals that measure real physical conditions are sampled into digital numeric values that can be manipulated by a computer.
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This process of sampling signals is called data acquisition: it converts analog waveforms into digital values for processing.
Commonly most electronic devices use semiconductor components to perform electron control.
That is the reason why we are going to study PN junction and the implementations of diodes, transistors, LED and so on.
The study of semiconductors and PN junction is a branch of Solid State Physics.
Here is a table showing the scheduled activities and the general planning.
LU PLANNING
STEP
PLACE
METHOD-ACTIVITIES
1.
Classroom with Lim and laptop in Interactive lesson; creation of a mind map with cmap.
a.Introduction and Motivation:
WiFi
Glossary
b.Brainstorming
c.Focus on vocabulary
2.Lecture I
Classroom with Lim and laptop in Interactive lesson: presentation with Prezi;
from 1 to 24 slide
WiFi
download of the ppt version for students;
discussion and questions.
3.
Classroom with Lim and laptop in Revision with a video
a.Video PN junction slide 25
WiFi
Consolidation activities in group work
b.Crossword activity
c.FCE activity
4.Lecture II
Classroom with Lim and laptop in Interactive lesson: presentation with Prezi;
from 26 to 37 slide
WiFi
discussion and questions.
5.Written test I
6.
a.Video Transistors slide 38
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TIME
1H
1,5H
+
0,5H
1H
2,0H
+
0,5H
Classroom with Lim and laptop in Individual test: problem solving, fill in, true/false, 1H
WiFi
multiple choice activities
Assessment: rubric enclosed
IT Laboratory
A video aimed at a deeper learning of the topic
1,5H
Group work aimed at a presentation for the oral test
2
b.Webquest
7.Oral test:
transistors
presentation
Further written test
Further oral test
Search for information in the web
about Classroom with Lim and laptop in Group work
WiFi
Creation of an interactive product
Assessment: rubric enclosed
Classroom
Problem solving for the simulation of Terza Prova
Classroom with Lim and laptop in Knowledge, skills, competences
WiFi
Assessment: rubric enclosed
2H
1H
3H
STEP 1. b. BRAINSTORMING
The map introduces the basic glossary related to PN junction and to the topics to be developed. It is also a hint for further key words students can
suggest and a way to enlarge their scientific vocabulary.
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STEP 1. c. FOCUS VOCABULARY
This step is aimed at consolidating the vocabulary necessary to fully understand the teacher’s lectures.
GLOSSARY
Band gap=the difference in energy between electron orbitals in which the electrons are not free to move (called valence bands) and orbitals in
which they are relatively free and can carry a current (called conduction bands).
Blur=become visually indistinct.
Breakdown=the abrupt failure of an insulator or insulating medium to restrict the flow of current.
Buildup=to form by combining materials or parts; construct.
Cease=put an end to, to come to an end.
Clip=cut, cut off.
Conduction band=the set of electron orbitals, generally the outermost shells of the atoms in a conductor or semiconductor, in
which electrons are free to move and thereby carry an electric current.
Departure=the act or an instance of departing.
Depletion layer=a region at the interface between dissimilar zones of conductivity in a semiconductor, in which there are few charge carriers.
Device=a machine or tool used for a specific task.
Diode=an electronic device that restricts current flow chiefly to one direction.
Dope=treat a semiconductor with an additive, dopant, used to improve its properties.
Dramatic =striking; effective
Dramatically=in a very impressive manner
Drop=In electronics to fall from a higher to a lower electric potential.
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Extrinsic semiconductor =an extrinsic semiconductor is a semiconductor that has been doped, that is, into which a doping agent has been
introduced, giving it different electrical properties than the intrinsic (pure) semiconductor.
Fermi level=the top of the available electron energy levels at low temperatures.
Forwardbias=a voltage applied to a circuit or device, esp. a semiconductor device, in the direction that produces the larger current.
Hole=a vacant position in an atom left by the absence of a valence electron.
Intrinsic=a semiconductor which is not doped.
Intrinsic semiconductor=an almost pure semiconductor to which no impurities have been added and in which the electron and hole
densities are equal at thermal equilibrium.
Lattice=an array of atoms, ions, etc, in a crystal or an array of points indicating their positions in space.
Overlap=have one or more elements in common.
Piecewise-linear=linear at intervals.
PN Junction=a transition region between regions of differing electrical properties in a semiconductor.
Provide=make available (something needed or desired); furnish.
Rectifier=an electronic device, such as a semiconductor diode or valve, that converts an alternating current to adirect current by suppression or
inversion of alternate half-cycles.
Reversebias=a voltage applied to a circuit or device, esp a semiconductor device, in the direction that blocks the passage of the current.
Ripple=a small wave, an undulation.
Room temperature=an indoor temperature around 20 or 22°C
Sample=represent the value of (an analog signal) at a particular point in time by means of a piece of digital data.
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Semiconductor=any of various solid crystalline substances, such as germanium or silicon, having electrical conductivity greater than insulators but
less than good conductors, and used especially as a base material for computer chips and other electronic devices.
Silicon=a nonmetallic element occurring extensively in the earth's crust in silica and silicates and used doped or in combination with other materials
in glass, semiconducting devices.
Slope=a.(of a line) the tangent of the angle between the line and another line parallel to the x-axis;
b. the first derivative of the equation of a curve at a given point.
Split=separate, divide.
Supply =verb make available or provide noun a source of electrical energy.
Swing=a regular movement up or down.
Switch=a device for turning on or off or directing an electric current.
Transformer=a device that transfers an alternating current from one circuit to one or more other circuits, usually withan increase (step-up
transformer) or decrease (step-down transformer) of voltage. The input current is fed to a primary winding, the output being taken from a secondary
winding or windings inductively linked to the primary.
Transistor =three-terminal, solid-state electronic device used for amplification and switching.
Turn on=cause to begin the operation, activity.
Valence band=the outermost electron shell of atoms in an insulator or semiconductor in which the electrons are too tightly
bound tothe atom to carry electric current.
Wire=to attach or connect with electrical wire or cable
Yield=to give up (an advantage, for example) to another
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STEP 2. Lecture I from 1 to 24 slide
This step is the first part of the lecture about PN junction. The topics are Band theory of solids, Intrinsic and extrinsic semiconductors,
What are P-type and N-type semiconductors, What are Diodes, Forward Bias & Reverse Bias, I – V Characteristics of Ideal Diodes. The lecture is
interactive using a Prezi presentation projected on the Lim. I have chosen this software because it is an engaging way to capture the attention of the
students and it also gives the possibility to enhance the interactive quality of the lecture. Moreover it is an effective possible tool for them to present
their own exam project.
During the presentation I am going to put some questions in order to test their attention and comprehension.
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Here are some problem solving activities to clarify the main points of the presentation.
Problem solving activities
1.Determine the diode voltage, the current and the potential difference across the resistor for the following circuits.
a.
b.
c.
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2.Which kind of output do you expect? Try to draw the output voltage across the diode.
Problem solving activities KEY
1.Determine the diode voltage, the current and the potential difference across the resistor for the following circuits.
a.
(1 mA)
b.
(86mA)
c.
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(16mA)
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2.Which kind of output do you expect? Try to draw the output voltage across the diode.
Solution
STEP 3. a. Video PN junction slide 25
This is a revision and consolidation step using a video about PN junction and diodes which helps students to clarify and consolidate some basic
points of lecture above.
https://youtu.be/W6QUEq0nUH8 (4:07)
STEP 3. b. Crossword activity
Now I divide the students into 5 groups of 4 and I assign them tasks and roles. Then I give them copies of the crossword. They have to complete it
in 15 minutes. I created the crossword using the free source eclipse crossword.
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PN junction
Across
3.
4.
5.
A voltage applied to a circuit or device, esp a semiconductor device, in the direction that produces the larger current
To treat a semiconductor with an additive used to improve its properties.
The difference in energy between electron orbitals in which the electrons are not free to move (called valence bands) and orbitals in which they
are relatively free and can carry a current (called conduction bands).
7. Any of various solid crystalline substances, such as germanium or silicon, having electrical conductivity greater than insulators but less than
good conductors, and used especially as a base material for computer chips and other electronic devices.
8. A transition region between regions of differing electrical properties in a semiconductor.
9. An array of atoms, ions, etc, in a crystal or an array of points indicating their positions in space.
10. A vacant position in an atom left by the absence of a valence electron.
11. A voltage applied to a circuit or device, esp a semiconductor device, in the direction that blocks the passage of the current.
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13. A semiconductor which is not doped.
14. A machine or tool used for a specific task.
Down
1.
2.
4.
6.
A region at the interface between dissimilar zones of conductivity in a semiconductor, in which there are few charge carriers.
The abrupt failure of an insulator or insulating medium to restrict the flow of current.
An electronic device that restricts current flow chiefly to one direction.
A nonmetallic element occurring extensively in the earth's crust in silica and silicates and used doped or in combination with other materials in
glass, semiconducting devices.
12. To form by combining materials or parts; construct.
Here is the solution to be discussed at the end of the activity.
PN junction key
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Across
3.
4.
5.
7.
8.
9.
10.
11.
13.
14.
FORWARDBIAS—A voltage applied to a circuit or device, esp a semiconductor device, in the direction that produces the larger current
DOPE—To treat a semiconductor with an additive used to improve its properties.
BANDGAP—The difference in energy between electron orbitals in which the electrons are not free to move (called valence bands) and
orbitals in which they are relatively free and can carry a current (called conduction bands).
SEMICONDUCTOR—Any of various solid crystalline substances, such as germanium or silicon, having electrical conductivity greater than
insulators but less than good conductors, and used especially as a base material for computer chips and other electronic devices.
PNJUNCTION—A transition region between regions of differing electrical properties in a semiconductor.
LATTICE—An array of atoms, ions, etc, in a crystal or an array of points indicating their positions in space.
HOLE—A vacant position in an atom left by the absence of a valence electron.
REVERSEBIAS—A voltage applied to a circuit or device, esp a semiconductor device, in the direction that blocks the passage of the current.
INTRINSIC—A semiconductor which is not doped.
DEVICE—A machine or tool used for a specific task.
Down
1.
DEPLETIONLAYER—A region at the interface between dissimilar zones of conductivity in a semiconductor, in which there are few charge
carriers.
2. BREAKDOWN—The abrupt failure of an insulator or insulating medium to restrict the flow of current.
4. DIODE—An electronic device that restricts current flow chiefly to one direction.
6. SILICON—A nonmetallic element occurring extensively in the earth's crust in silica and silicates and used doped or in combination with other
materials in glass, semiconducting devices.
12. BUILDUP—To form by combining materials or parts; construct.
STEP 3. c. FCE activity
The following activities are a FCE reading and comprehension activity part 6, gapped text and a cloze test. The suggested time is 15 minutes each.
FCE Reading- Part 6 –Gapped text
You are going to read an article about PN junction. Seven sentences have been removed from the article. Choose from the sentences A – H the one
which fits each gap (1-7). There is one extra sentence you do not need to use.
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A
This energy difference is called a band gap.
B
A voltage or current applied to one pair of the transistor's terminals changes the current
through another pair of terminals.
C
has four valence electrons, each of which participates in a bond in the crystal lattice.
D
In doing so, they leave vacancies (holes), which may then be filled by other electrons, thus
allowing the electrons to move about the crystal lattice of the material, and a current to flow.
E
One can increase the electrical conductivity of a semiconductor by doping it with a small
amount of certain other elements
F
Thus, doping silicon with a small amount of arsenic produces an n-type semiconductor.
G
Most LEDs that have a round case have a longer lead on the anode than on the cathode, and a
flat near the cathode lead.
H
Such materials are called semiconductors.
PN Junction
The schematic symbol for a diode is:
diode
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light-emitting diode (LED)
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As the symbols are oriented above, the wire on the left goes to the anode, and the wire on the right goes to the cathode. (1)…………………
How does it work?
Materials are often broadly classified as conductors or insulators. For a substance to be a conductor, its electronic structure must be such that there
are unoccupied energy levels close enough in energy to where the valence electrons normally reside that the electrons can easily be excited to those
levels. (2)………………… These energy levels comprise what is commonly called the conduction band. The levels occupied by the unexcited
valence electrons are known as the valence band. In an insulator, the conduction band lies at sufficiently high energy above the valence band that
the valence electrons cannot easily reach the levels that lie there, and the material does not conduct electricity. (3)………………… In some
materials, the band gap is much smaller than that of an insulator, and the electrical conductivity is intermediate between that of a conductor and that
of an insulator. (4)…………………
The most commonly used elements in semiconductor devices are probably silicon and germanium. (5)…………………that have either one more or
one fewer valence electron than does the semiconductor in question. For example, silicon, which is in qroup IV, (6)…………………. If an arsenic
atom, which has five valence electrons, replaces a silicon atom, it then has one electron left over, which cannot participate in bonding and is thus
available for conduction. (7)………………… If, instead, one substitutes some boron atoms, which have only three valence electrons, this results in
electron vacancies in the crystal lattice, or holes. When an electron moves to fill one of these holes, it leaves behind another hole. This type of
semiconductor is called p-type. Thus, we speak of the charge carriers in n-type material as being electrons, and in p-type material as being holes.
(Abridged from http://web.physics.ucsb.edu/~lecturedemonstrations/Composer/Pages/64.56)
FCE Open close – Part 2
For questions 1-20, read the text below and think of the word which best fits each gap. Use only one word in each gap.
The simplest semiconductor (1)………………... is a p-n junction. That is, a piece of p-type material and a piece of n-type material placed in
contact with each other. If no external potential is applied, some of the electrons in the n-type material can cross the junction to fill holes in the ptype material. This leaves a (2)………………... charge on the n-type section and a (3)………………... charge on the p-type section, which
prevents further flow of charge carriers across the junction. The resulting potential is (4)………………... the contact potential or junction
potential. We will see that we must overcome this junction potential in order to make the diode (5)………………... electricity.
If we (6)………………... bias the junction, that is, place a potential across it so that the n-type section is positive with respect to the p-type section,
any (7)………………... in the p-type region cross back over the junction into the n-type region, where all the electrons are drawn
(8)………………... from the junction towards the positive supply terminal. Similarly, any (9)………………... that were in the n-type region are
filled, and the holes in the p-type region are drawn towards the negative terminal. The junction is thus (10)………………... of charge carriers, and
current (11)………………... flow.
If we bias the junction in the (12)………………... direction, that is, put a potential across it so that the p-type section is now positive with respect
to the n-type section, the (13)………………... in the n-type material are repelled from the negative power (14)………………... terminal, as are the
holes in the p-type region repelled from the positive terminal. The electrons in the n-type region are drawn towards the (15)………………... ,
which they can now cross to fill the holes in the p-type region, leaving more holes behind in the n-type region. Current can now
(16)………………... , and the diode conducts. Since the above mentioned junction potential is opposite to the forward bias potential, whatever
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potential we (17)………………... must exceed this junction potential in order for the (18)………………... to conduct. The (19)………………...
is, of course, the n-type region, and the (20)………………... is the p-type region.
(Abridged from http://web.physics.ucsb.edu/~lecturedemonstrations/Composer/Pages/64.56)
Here is the solution to be discussed at the end of the activity.
KEYS
FCE Reading- Part 6 –Gapped text
A
B
C
D
E
F
G
H
This energy difference is called a band gap.
A voltage or current applied to one pair of the transistor's terminals changes the current
through another pair of terminals. EXTRA
has four valence electrons, each of which participates in a bond in the crystal lattice.
In doing so, they leave vacancies (holes), which may then be filled by other electrons, thus
allowing the electrons to move about the crystal lattice of the material, and a current to flow.
One can increase the electrical conductivity of a semiconductor by doping it with a small
amount of certain other elements
Thus, doping silicon with a small amount of arsenic produces an n-type semiconductor.
Most LEDs that have a round case have a longer lead on the anode than on the cathode, and a
flat near the cathode lead.
Such materials are called semiconductors.
FCE Open close – Part 2
The simplest semiconductor device is a p-n junction. That is, a piece of p-type material and a piece of n-type material placed in contact with each
other. If no external potential is applied, some of the electrons in the n-type material can cross the junction to fill holes in the p-type material. This
leaves a positive charge on the n-type section and a negative charge on the p-type section, which prevents further flow of charge carriers across the
junction. The resulting potential is called the contact potential or junction potential. We will see that we must overcome this junction potential in
order to make the diode conduct electricity.
If we reverse bias the junction, that is, place a potential across it so that the n-type section is positive with respect to the p-type section, any
electrons in the p-type region cross back over the junction into the n-type region, where all the electrons are drawn away from the junction towards
the positive supply terminal. Similarly, any holes that were in the n-type region are filled, and the holes in the p-type region are drawn towards the
negative terminal. The junction is thus depleted of charge carriers, and current cannot flow.
If we bias the junction in the forward direction, that is, put a potential across it so that the p-type section is now positive with respect to the n-type
section, the electrons in the n-type material are repelled from the negative power supply terminal, as are the holes in the p-type region repelled from
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the positive terminal. The electrons in the n-type region are drawn towards the junction, which they can now cross to fill the holes in the p-type
region, leaving more holes behind in the n-type region. Current can now flow, and the diode conducts. Since the above mentioned junction potential
is opposite to the forward bias potential, whatever potential we apply must exceed this junction potential in order for the diode to conduct. The
cathode is, of course, the n-type region, and the anode is the p-type region.
STEP 4. Lecture II from 26 to 37 slide
This step is the second part of the lecture about PN junction. The topics are Half wave rectifier with a simple diode, Half wave rectifier with a CR
circuit, Full wave rectifier: bridge rectifier, Light emitting diode: LED. The lecture is interactive using a Prezi presentation projected on the Lim. I
have chosen this software because it is an engaging way to capture the attention of the students and it also gives the possibility to enhance the
interactive quality of the lecture. Moreover it is an effective possible tool for them to present their own exam project.
During the presentation I am going to put some questions in order to test their attention and comprehension.
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STEP 5. Written test I
In this phase it is necessary to test the students’ skills and competences. The written test consists of problem solving, fill in, true/false, multiple
choice activities.
PHYSICS WRITTEN TEST
Date : ……….
Topic: PN junction, diodes
Name: _______________________
Class 5C
Pass 90 points
Multiple choice activity: you are forbidden to erase and change your written choice
Multiple choice + Filling the blanks activities score : 116/150
4 points for each right choice
0 point for each wrong choice
1 point for each missing choice
Give reasons of the choice if requested, or it is invalid
True / False activity score:4/150
1 point for each right choice
0,5 point for each missing choice
0 point for each wrong choice
Problem score: 30/150, see the enclosed rubric
1.When matching polarity connections have been made and the potential difference (PD) is above 0.7 V, the diode is considered to be:
A. not working
B. forward biased
C. reverse biased
D. an open switch
2.What is the current through the LED?
A. 0 mA
B. 23 mA
C. 18 mA
D. 13 mA
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3.Since diodes are destroyed by excessive current, circuits must have:
A. higher voltage sources
B. current limiting resistors
C. more dopants
D. higher current sources
4.Testing a good diode with an ohmmeter should indicate
A. high resistance when forward or reverse biased
B. low resistance when forward or reverse biased
C. high resistance when reverse biased and low resistance when forward biased
D. high resistance when forward biased and low resistance when reverse biased
5.What is the current through the diode?
A. 1 mA
B. 0.975 mA
C. 0.942 mA
D. 0.0 mA
6.A pn junction allows current flow when
A. the p-type material is more positive than the n-type material
B. the n-type material is more positive than the p-type material
C. both the n-type and p-type materials have the same potential
D. there is no potential on the n-type or p-type materials
7.When a diode is forward biased, the voltage across it
A. is directly proportional to the current
B. is inversely proportional to the current
C. is directly proportional to the source voltage
D. remains approximately the same
8.With a 12 V supply, a silicon diode, and a 370-ohm resistor in series, what voltage will be dropped across the diode?
A. 0.3 V
B. 0.7 V
C. 0.9 V
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D. 1.4 V
9. The area at the junction of p-type and n-type materials that has lost its majority carriers is called the
A. barrier potential
B. depletion region
C. n region
D. p region
10.DC power should be connected to forward bias a diode as follows:
A. – anode, + cathode
B. – cathode, – anode
C. + anode, – cathode
D. + cathode, + anode
11.At any given time in an intrinsic piece of semiconductor material at room temperature
A. electrons drift randomly
B. recombination occurs
C. holes are created
D. All of the above
12.A reverse biased diode will act as an open switch.
A. True
B. False
13. If the diode in a series circuit is reverse biased, the resistor will drop all the applied voltage. A.True
B. False
14.
Reverse biasing a pn junction allows the flow of majority current.
A.True
B. False
15.Doping semiconductive material is the process of putting a small amount of pentavalent or trivalent atoms in with tetravalent atoms.
A.True
B. False
16.
A ___ is created when an electron moves from the valence band to the conduction band.
A. hole
B. gap
C. vacancy
D. blank
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17.Typically the forward voltage on an LED is between _______ and ________.
A. 1.5 V, 3.7 V
B. 0.7 V, 1.1 V
C. 1 V, 3 V
D. 1 V, 6 V
18.
The name of the circuit in the given circuit is the ___.
A. half-wave rectifier
B. center-tapped full-wave rectifier
C. full-wave bridge rectifier
D. half-wave bridge rectifier
19.The small amount of ac signal present on the output of a filtering network for a dc power supply is known as ________.
A. pulsating dc
B. trickle
C. ripple
D. waffle
20.
Atoms in a silicon crystal are held together by ___ bonds.
A. crystal
B. chemical
C. electrical
D. covalent
21.The peak output voltage from the circuit in the given circuit equals
A. 3 V
B. 3.7 V
C. 2.3 V
D. 0 V
___.
22.An electron can move to another atom's orbit only while in the _______.
A. valence band
B. conduction band
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C. orbit nearest the nucleus
D. covalent band
23.___ occurs when a pn junction is first formed.
A. Recombination
B. Covalent bonding
C. Crystallization
D. Breakdown
24.Connecting a capacitor filter to the circuit in the given circuit will___.
A. produce a nearly-constant dc voltage
B. reduce the output voltage
C. increase the ripple voltage
D. lower the surge current
25.A pure semiconductor material ___ very well.
A. conducts
B. insulates
C. conducts and insulates
D. neither conducts nor insulates
26.Single-element semiconductors are characterized by atoms with ____ valence electrons.
A. 3
B. 4
C. 5
D. 2
27.Under normal conditions a diode conducts current when it is
A. reverse-biased.
B. forward-biased.
C. avalanched.
D. saturated.
28. A diode conducts when it is forward-biased, and the anode is connected to the ________ through a limiting resistor.
A. positive supply
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B. negative supply
C. cathode
D. anode
29.An n-type semiconductor material
A. is intrinsic.
B. has trivalent impurity atoms added.
C. has pentavalent impurity atoms added.
D. requires no doping.
30.The boundary between p-type material and n-type material is called
A. a diode.
B. a reverse-biased diode.
C. a pn junction.
D. a forward-biased diode.
31.What types of impurity atoms are added to increase the number of conduction-band electrons in intrinsic silicon?
A. bivalent
B. octavalent
C. pentavalent
D. trivalent
32.Doping of a semiconductor material means
A. that a glue-type substance is added to hold the material together.
B. that impurities are added to increase the resistance of the material.
C. that impurities are added to decrease the resistance of the material.
D. that all impurities are removed to get pure silicon.
33.The forward voltage across a conducting silicon diode is about
A. 0.3 V.
B. 1.7 V.
C. –0.7 V.
D. 0.7 V.
34.Which lamps are alight? Some may not be full brightness.
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(30 points)
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Draw other two circuits, which simulate the behaviour of the circuits above at the best, showing only the lighting lamps. Give reasons for the choice
you made.
Which are the brightest lamps?
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INDICATORS
DESCRIPTION OF SKILLS
LOGIC AND
INSIGHT SKILLS
AND
COMPETENCES
SOLUTION
STRATEGY
CONTENT
Score
40%
40%
20%
Knowledge of principles, theories, concepts, laws,
rules, methods and procedures, scientific
terminology
Score
Organization and use of means, skills and
competences aimed at analyzing, dividing into
steps, calculating data.
Sentence flow, sentence structure and grammar,
terminology used.
Coherence and cohesion in the insight.
Score
28
12
Individual score
Individual score
KEY
Date : ……….
Topic: PN junction, diodes
Laurena Petrizzi LS A. Oriani Ravenna
Individual score
Right calculations and reasoning, strategy choice.
Accuracy in pictures, schemes, graphic
representations and diagrams.
Use of notations and scientific means to represent
the information.
PHYSICS WRITTEN TEST
12
6
Name: _______________________
Class 5C
Pass 90 points
Multiple choice activity: you are forbidden to erase and change your written choice
Multiple choice + Filling the blanks activities score : 116/150
4 points for each right choice
0 point for each wrong choice
1 point for each missing choice
Give reasons of the choice if requested, or it is invalid
True / False activity score:4/150
1 point for each right choice
0,5 point for each missing choice
0 point for each wrong choice
Problem score: 30/150, see the enclosed rubric
1.When matching polarity connections have been made and the potential difference (PD) is above 0.7 V, the diode is considered to be:
A. not working
B. forward biased
C. reverse biased
D. an open switch
2.What is the current through the LED?
A. 0 mA
B. 23 mA
C. 18 mA
D. 13 mA
3.Since diodes are destroyed by excessive current, circuits must have:
A. higher voltage sources
B. current limiting resistors
C. more dopants
D. higher current sources
4.Testing a good diode with an ohmmeter should indicate
Laurena Petrizzi LS A. Oriani Ravenna
29
A.
B.
C.
D.
high resistance when forward or reverse biased
low resistance when forward or reverse biased
high resistance when reverse biased and low resistance when forward biased
high resistance when forward biased and low resistance when reverse biased
5.What is the current through the diode?
A. 1 mA
B. 0.975 mA
C. 0.942 mA
D. 0.0 mA
6.A pn junction allows current flow when
A. the p-type material is more positive than
B. the n-type material is more positive than the p-type material
C. both the n-type and p-type materials have the same potential
D. there is no potential on the n-type or p-type materials
the n-type material
7.When a diode is forward biased, the voltage across it
A. is directly proportional to the current
B. is inversely proportional to the current
C. is directly proportional to the source voltage
D. remains approximately the same
8.With a 12 V supply, a silicon diode, and a 370-ohm resistor in series, what voltage will be dropped across the diode?
A. 0.3 V
B. 0.7 V
C. 0.9 V
D. 1.4 V
9. The area at the junction of p-type and n-type materials that has lost its majority carriers is called the
A. barrier potential
B. depletion region
C. n region
D. p region
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10.DC power should be connected to forward bias a diode as follows:
A. – anode, + cathode
B. – cathode, – anode
C. + anode, – cathode
D. + cathode, + anode
11.At any given time in an intrinsic piece of semiconductor material at room temperature
A. electrons drift randomly
B. recombination occurs
C. holes are created
D. All of the above
12.A reverse biased diode will act as an open switch.
A. True
B. False
13.If the diode in a series circuit is reverse biased, the resistor will drop all the applied voltage.
A.True
B. False
14.
Reverse biasing a pn junction allows the flow of majority current.
A.True
B. False
15.Doping semiconductive material is the process of putting a small amount of pentavalent or trivalent atoms in with tetravalent atoms.
A.True
B. False
16.
A ___ is created when an electron moves from the valence band to the
A. hole
B. gap
C. vacancy
D. blank
17.Typically the forward voltage on an LED is between _______ and ________.
A. 1.5 V, 3.7 V
B. 0.7 V, 1.1 V
C. 1 V, 3 V
D. 1 V, 6 V
18.The name of the circuit in the given circuit is the___.
A. half-wave rectifier
Laurena Petrizzi LS A. Oriani Ravenna
31
conduction band.
B. center-tapped full-wave rectifier
C. full-wave bridge rectifier
D. half-wave bridge rectifier
19.The small amount of ac signal present on the output of a filtering network for a dc power supply is known as ________.
A. pulsating dc
B. trickle
C. ripple
D. waffle
20.
Atoms in a silicon crystal are held together by ___ bonds.
A. crystal
B. chemical
C. electrical
D. covalent
21.
The peak output voltage from the circuit in the given
A. 3 V
B. 3.7 V
C. 2.3 V
D. 0 V
circuit equals ___.
22.An electron can move to another atom's orbit only while in the _______.
A. valence band
B. conduction band
C. orbit nearest the nucleus
D. covalent band
23.___ occurs when a pn junction is first formed.
A. Recombination
B. Covalent bonding
C. Crystallization
Laurena Petrizzi LS A. Oriani Ravenna
32
D. Breakdown
24.
Connecting a capacitor filter to the circuit in the given
A. produce a nearly-constant dc voltage
B. reduce the output voltage
C. increase the ripple voltage
D. lower the surge current
circuit will___.
25.A pure semiconductor material ___ very well.
A. conducts
B. insulates
C. conducts and insulates
D. neither conducts nor insulates
26.Single-element semiconductors are characterized by atoms with ____ valence electrons.
A. 3
B. 4
C. 5
D. 2
27.Under normal conditions a diode conducts current when it is
A. reverse-biased.
B. forward-biased.
C. avalanched.
D. saturated.
28. A diode conducts when it is forward-biased, and the anode is connected to the ________ through a limiting resistor.
A. positive supply
B. negative supply
C. cathode
D. anode
29.An n-type semiconductor material
A. is intrinsic.
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B. has trivalent impurity atoms added.
C. has pentavalent impurity atoms added.
D. requires no doping.
30.The boundary between p-type material and n-type material is called
A. a diode.
B. a reverse-biased diode.
C. a pn junction.
D. a forward-biased diode.
31.What types of impurity atoms are added to increase the number of conduction-band electrons in intrinsic silicon?
A. bivalent
B. octavalent
C. pentavalent
D. trivalent
32.Doping of a semiconductor material means
A. that a glue-type substance is added to hold the material together.
B. that impurities are added to increase the resistance of the material.
C. that impurities are added to decrease the resistance of the material.
D. that all impurities are removed to get pure silicon.
33.The forward voltage across a conducting silicon diode is about
A. 0.3 V.
B. 1.7 V.
C. –0.7 V.
D. 0.7 V.
34.Which lamps are alight? Some may not be full brightness.
Laurena Petrizzi LS A. Oriani Ravenna
(30 points)
34
Draw other two circuits, which simulate the behaviour of the circuits above at the best, showing only the lighting lamps. Give reasons for the choice
you made.
Which are the brightest lamps?
Laurena Petrizzi LS A. Oriani Ravenna
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STEP 6. a. Video Transistors slide 38
This step engages the students to go deep into the topic using their own skills and competences to find out further information about other electronic
components. They will be able to do it using video about transistors and a webquest activity in the IT lab.
https://youtu.be/FODFowmDfvY (6:29)
To start the webquest the students are given a problem through questions:
What is a transistor?
Can you trace a brief history of transistors?
How many kinds of transistor are available?
How are transistors made?
What are the functions of a transistor?
The suggested sources for the webquest are:
http://www.bbc.co.uk/schools/gcsebitesize/design/electronics/switchesrev3.shtml
https://en.wikipedia.org/wiki/Transistor
http://www.nobelprize.org/educational/physics/transistor/function/index.html
https://en.wikibooks.org/wiki/Semiconductors/Introduce_to_Transistor
https://www.youtube.com/watch?v=FODFowmDfvY
https://www.youtube.com/watch?v=CkX8SkTgB0g
https://www.youtube.com/watch?v=4QkRI1Ue208
https://www.youtube.com/watch?v=SjeK1nkiFvI
https://www.youtube.com/watch?v=W6QUEq0nUH8
They are also given the following task:
Create a presentation in PREZI, PPT, KEYNOTE, etc. following the outline above.
Specify the sources used following the hints from http://www.unive.it/nqcontent.cfm?a_id=39026
The students have a week to complete the work.
I enclose the rubric for the assessment of the oral presentation.
Laurena Petrizzi LS A. Oriani Ravenna
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Rubric - Presenter Skills and Attributes in Scientific Oral Presentation
Laurena Petrizzi LS A. Oriani Ravenna
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Further written
test
Problem solving for the simulation of Terza Prova
DESCRIPTION OF SKILLS – ATTRIBUTES – COMPETENCES
INDICATORS
SCORE
ORGANIZATION-PLANNING
 Planning
 Use of schemes, diagrams, maps
 Slide order




Very poor/poor planning skills, competences
Acceptable/passing planning skills, competences
Adequate planning skills, competences
Good/Excellent planning skills, competences
0.5
1
1.5
2
ACCURACY
 Slide numbers
 Date
 Footer
 Bibliography/sources/references



Poor/partly adequate accuracy
Adequate accuracy
Good/Excellent accuracy
0.5
1
1.5
CONTENT
 Understanding of theme and
relationship to topic
 Use of supporting examples or
details
 Organization, sentence structure
and grammar
 Appropriate use of terminology
(scientific vocabulary)
 Pronunciation
 Synthesis

Poor/confused organization, grammatical, spelling and pronunciation errors, difficulty in
expressing ideas and information, recurrent hesitations, incorrect terminology, very poor,
understanding of theme, lacking or incorrect examples/details
Acceptable/passing, some organizational and grammatical problems, passing use of
terminology and pronunciation, evidence of limited understanding, minimal examples and
details
Adequate, minimal errors and mistakes, adequate terminology and pronunciation, evidence of
a basic understanding and synthesis, adequate supporting examples and/or details
Good sentence flow, sentence structure and grammar, good pronunciation, terminology
correctly used, evidence of good understanding and synthesis, examples or/and details
generally well applied to theme
Very good/Excellent, excellent organization, sentence structure and grammar, accurate
scientific terminology, very good pronunciation, evidence of full and complete understanding,
well chosen examples, accurate details applied to theme




ICT





Use of the chosen software
Graphic design
Graphics/use of images
Hyperlinks/Links
Use of transitions and animations



Individual score
1.5
2.5
3
4
5
0.5
1
1.5
Poor/Adequate technical skills and competences
Adequate technical skills and competences
Good/Excellent technical skills and competences
Totale:
GIUDIZIO
Insuff. molto
grave-impreparato
Voto in 1/10
1-3
Laurena Petrizzi LS A. Oriani Ravenna
Insuff. grave
raggiungimento
minimi
4 - 4.5
con mancato Insuff. non grave con parziale raggiungimento Sufficiente
degli obiettivi degli obiettivi
5 - 5.5
6
38
Discreto
Buono
Ottimo/
Eccellente
6.5 - 7
7.5 - 8.5
9 - 10
1) What do you mean by N-type and P-type semiconductors and what is the most important difference between an intrinsic and an extrinsic
semiconductor? What happens when you make a PN junction? When do you have a forward bias or a reverse bias connection?
a.Can you identify which diode is conducting in this circuit and can you explain why?
or
b.Assuming D1 and D2 are ideal diodes. What is the current flowing in the diode D2 and what is the potential difference across the same diode?
2) Can you draw the peak rectifier circuit using a diode with CR filter and can you briefly describe and explain how it works?
3) With reference to its volt ampere characteristic, can you explain how a silicon diode can be used to rectify a double-wave signal into a half-wave
signal?
Further oral test
Laurena Petrizzi LS A. Oriani Ravenna
39
INDICATORS
Coherence-Cohesion
Discourse management
 Coherence, cohesion and fluency
 Discourse management
DESCRIPTION OF SKILLS – ATTRIBUTES – COMPETENCES
SCORE
Lack of cohesion and coherence, difficult communication often teacher-led,
inadequate discourse management
0.5
Adequate discourse management
1
Excellent fluency and discourse management
1.5
Grammar, vocabulary, pronunciation
 Organization, sentence structure and grammar
 Appropriate use of terminology
 Pronunciation
Poor organization grammatical, spelling and pronunciation errors, difficulty in
expressing ideas and information, recurrent hesitations, incorrect terminology
Some organizational and grammatical problems, adequate terminology and
pronunciation
Good sentence flow, sentence structure and grammar, good pronunciation,
terminology correctly used
Excellent organization, sentence structure and grammar, accurate scientific
terminology, very good pronunciation
Content
 Understanding of theme and relationship to topic
 Use of supporting examples or details
 Synthesis
Very poor, no understanding of theme, lacking or incorrect examples/details
Poor, evidence of limited understanding, minimal examples and details
Adequate, evidence of a basic understanding and synthesis, adequate supporting
examples and/or details
Good, evidence of good understanding and synthesis, examples or/and details
generally well applied to theme
Excellent, evidence of full and complete understanding, well chosen examples,
accurate details applied to theme
Difficult interaction among the students and between a student and the teacher
Adequate interaction but essential and simple
Good interaction among the speakers without any interruption and in turn
Excellent interaction and discourse organization
Interactive communication
 Interaction
 Communicative skills
Individual score
0.5
1
1.5
2
1.5
2
3
4
4.5
0.5
1
1.5
2
Assessment
GIUDIZIO
Voto in 1/10
Totale:
Insuff. , molto
grave-impreparato
1-3
Laurena Petrizzi LS A. Oriani Ravenna
Insuff. , grave con Insuff. non grave con parziale raggiungimento Sufficiente
mancato raggiungimento degli obiettivi
degli obiettivi minimi
4 - 4.5
5 - 5.5
6
40
Discreto
6.5 - 7
Buono
7.5 -8.5
Ottimo/
Eccellente
9 - 10