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American System Physics

A Physics Toolkit

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Representing Motion

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Accelerated Motion

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Forces in One Dimension

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Displacement and Force in Two Dimensions

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Motion in Two Dimensions

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Gravitation

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Rotational Motion

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Momentum and Its Conservation

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Energy and Its Conservation

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Thermal Energy

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States of Matter

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Vibrations and Waves

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Sound

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Fundamentals of Light

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Reflection and Refraction

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Interference and Diffraction

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Electrostatics

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Electric Current and Circuits

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Magnetic Fields

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Electromagnetic Induction and Electromagnetism

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Quantum Theory and the Atom

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Solid-State Electronics

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Nuclear and Particle Physics

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Quiz

23.1 Conduction in Solids – Quiz

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Conduction in Solids American Physics quiz: free practice for American System Physics. Work through this Conduction in Solids American Physics quiz and get instant feedback on every answer. If you get stuck, review the 23.1 Conduction in Solids — Notes lesson. More practice: American System Physics — all units. Syllabus: OpenStax free science textbooks.

  • Questions count: 50
  • Passing grade: A-
  • Time limit:
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1.
The diagram shows the band structures of three solids P, Q and R. Which solid is a semiconductor?
Dr Dabour Hub Academy - figure 1
P
R
None of them
Q
2.
Using the band diagrams shown, which solid would have the most free charge carriers at room temperature?
Dr Dabour Hub Academy - figure 2
X
Y
Z
All three have the same number
3.
Using the band gaps shown, what is the longest wavelength of light that can free an electron across the gap in silicon?
Dr Dabour Hub Academy - figure 3
1855 nm
565 nm
1130 nm
1.81e-16 nm
4.
The graph shows how the resistances of two components change with temperature. Which conclusion is correct?
Dr Dabour Hub Academy - figure 4
Component 1 is a semiconductor, because its resistance rises with temperature
Both are metals, because resistance changes with temperature
Component 2 is an insulator, because its resistance is very high at low temperature
Component 2 is a semiconductor, because its resistance falls as temperature rises
5.
The graph shows the resistance of different lengths of one wire of cross-sectional area 2.0 x 10^-7 m^2. What is the resistivity of the metal?
Dr Dabour Hub Academy - figure 5
2.5 ohm m
1.2e+07 ohm m
5.0e-07 ohm m
8.0e-08 ohm m
6.
The graph shows the relative number of free electrons in pure silicon at different temperatures. What happens to its resistance as it is heated from 300 K to 350 K?
Dr Dabour Hub Academy - figure 6
It decreases, because the number of carriers increases several times
It increases, because lattice vibrations dominate
It stays the same, because silicon is pure
It increases, because holes are removed
7.
A student records the data in the table for an unknown sample. What type of material is it most likely to be?
A semiconductor
A metal
An insulator
A superconductor
8.
The table shows current in silicon samples with different amounts of phosphorus. What does the data show?
Doping has no effect on current
More dopant increases the resistance
More dopant gives more carriers and a larger current, so lower resistance
Current is independent of the dopant, but depends on p.d.
9.
Using the table, what is the resistance of the sample with 4 dopant atoms per 10^6 Si?
0.5 ohm
2.0 ohm
18 ohm
500 ohm
10.
In the experiment in the table, which variable must be kept constant for a fair comparison?
Sample temperature and dimensions
Dopant concentration
Current
The number of holes
11.
The table lists three solids. Which one is classified correctly?
Solid A - semiconductor
Solid C - insulator
Solid B - insulator
Solid C - conductor
12.
All three wires in the table have length 1.0 m and area 1.0 mm^2. What is the resistivity of nichrome?
1.1 ohm m
1.1 x 10^6 ohm m
1.1 x 10^-6 ohm m
1.1 x 10^-3 ohm m
13.
Green light of wavelength 500 nm has photons of energy 2.49 eV. Using the table, which material would NOT have electrons promoted across its gap by this light?
Ge
Si
GaAs
Diamond
14.
Using the table, by what factor does the resistance change between 25 deg C and 75 deg C?
It falls to 0.16 of its original value
It rises by a factor of 6.25
It falls to 0.5 of its original value
It does not change
15.
Which statement best defines the band gap of a solid?
The range of energies between the top of the valence band and the bottom of the conduction band that electrons cannot have
The energy needed to remove an electron completely from an isolated atom
The width of the valence band measured in electronvolts
The distance between neighbouring atoms in the crystal lattice
16.
Why do energy bands, rather than single energy levels, form in a solid?
Electrons in a solid can have any energy at all
The energy levels of many neighbouring atoms overlap and split into many closely spaced levels
Heating the solid spreads each energy level out
Only the outer electrons of each atom have energy levels
17.
Which band holds the electrons that are bound in the bonds between atoms?
Conduction band
Forbidden gap
Valence band
Depletion band
18.
What is a hole in a semiconductor?
A missing atom in the crystal lattice
A free proton that moves through the crystal
A vacancy in the valence band left when an electron moves to the conduction band, acting as a positive carrier
A gap in the conduction band where no energy levels exist
19.
A technician is choosing an impurity for silicon. Which dopant is matched with the correct majority carrier?
Gallium dopant - majority carriers are electrons
Boron dopant - donor atom
Phosphorus dopant - majority carriers are holes
Arsenic dopant - majority carriers are electrons
20.
A data book lists approximate resistivities. Which material is given its correct value?
Copper - about 1.7 x 10^-8 ohm m
Glass - about 1.7 x 10^-8 ohm m
Silicon - about 10^12 ohm m
Copper - about 10^3 ohm m
21.
Which statement correctly links a class of material to what its resistance does when warmed?
Metal - resistance decreases because more carriers are released
Semiconductor - resistance decreases because more carriers are released
Insulator - resistance falls to almost zero
Semiconductor - resistance increases because of lattice vibrations
22.
Which physical quantity is shown with its correct SI unit?
Resistivity - ohm per metre
Conductivity - ohm m
Conductivity - (ohm m)^-1
Resistivity - ohm m^2
23.
A copper wire is 2.0 m long with cross-sectional area 5.0 x 10^-7 m^2. Taking the resistivity of copper as 1.7 x 10^-8 ohm m, what is its resistance?
4.25e-15 ohm
0.068 ohm
68 ohm
0.017 ohm
24.
A 0.80 m test rod with a 2.0 x 10^-6 m^2 cross-section reads 4.0 ohm on a meter. Deduce the resistivity of the rod material.
1.00e-05 ohm m
1.60e+06 ohm m
6.40e-06 ohm m
2.50e+06 ohm m
25.
A doped semiconductor has resistivity 0.0025 ohm m. What is its conductivity?
0.0025 (ohm m)^-1
400 ohm m
400 (ohm m)^-1
1.6e+05 (ohm m)^-1
26.
A copper wire and a silicon rod have identical dimensions. Using copper about 1.7 x 10^-8 ohm m and silicon about 10^3 ohm m, roughly how many times larger is the silicon rod's resistance?
about 1000 times
about 1.7 x 10^-11 times
about the same
about 5.9e+10 times
27.
A wire is replaced by one of the same material with twice the length and twice the diameter. What happens to its resistance?
It halves
It doubles
It stays the same
It becomes four times larger
28.
A current of 0.25 A flows through a semiconductor sample for 40 s. How many electrons pass a point (e = 1.60 x 10^-19 C)?
1.00e+01
6.25e+19
1.56e+18
1.60e-18
29.
A potential difference of 6.0 V across a silicon sample drives a current of 15 mA. What is its resistance?
0.09 ohm
0.0025 ohm
0.4 ohm
400 ohm
30.
When a potential difference is applied to p-type silicon, which statement describes the carriers?
Holes drift towards the positive terminal
Holes drift towards the negative terminal and electrons towards the positive terminal
Only electrons move; holes are fixed
Both drift towards the positive terminal
31.
A student says, "Insulators never conduct because they have no electrons." Which is the best correction?
Insulators have many electrons, but they are held in a full valence band with a large gap to the conduction band
The student is correct
Insulators have electrons only in the conduction band
Insulators conduct only because of holes
32.
Reading the graph, the number of free electrons at 350 K is about _____ times that at 300 K.
Dr Dabour Hub Academy - figure 7
2
21
0.5
100
33.
Silicon doped with phosphorus is called a(n) _____ semiconductor.
p-type
intrinsic
insulating
n-type
34.
Atoms with three valence electrons, such as boron, added to silicon are called _____ atoms.
acceptor
donor
intrinsic
conductor
35.
In p-type silicon the majority charge carriers are _____.
electrons
holes
protons
positive ions
36.
Engineers cut a tiny silicon bar 1.0 cm long with a 1.0 mm^2 end face (resistivity 1.0 x 10^3 ohm m). Its resistance works out to _____.
1.0e+09 ohm
1.0e-01 ohm
1.0e+04 ohm
1.0e+07 ohm
37.
A photodiode passes a steady 3.2 mA for two minutes. The number of electrons that flow through it is _____.
4.0e+16
3.8e-01
2.4e+18
2.4e+21
38.
The diagram shows two samples. Sample 2 is an insulator because its band gap exceeds about 5 eV. True or false?
Dr Dabour Hub Academy - figure 8
False, because sample 2 is a metal
True
False, because a larger gap means more free electrons
True only when sample 2 is heated
39.
Refer to the graph. The rise in resistance of component 1 is best explained by increased lattice vibrations obstructing free electrons. True or false?
Dr Dabour Hub Academy - figure 9
True
False, because the number of free electrons falls
False, because component 1 is an insulator
True only below 293 K
40.
The graph of R against L passing through the origin shows that resistance is directly proportional to length. True or false?
Dr Dabour Hub Academy - figure 10
False, because R is inversely proportional to L
False, because it depends on current
True only for semiconductors
True
41.
The flow diagram correctly shows how adding phosphorus increases the conductivity of silicon. True or false?
Dr Dabour Hub Academy - figure 11
False, because phosphorus creates holes
False, because the fifth electron forms a bond
True
True only for boron
42.
From the table, the resistance roughly halves for every 20 deg C rise over the whole range. True or false?
True
False, because the ratio for each 20 deg C step is about 0.57 to 0.61, not 0.5
True only between 20 and 40 deg C
False, because the resistance increases
43.
Electrons in the conduction band are free to move through the solid and so can carry current. True or false?
False, because only holes carry current
False, because conduction-band electrons are fixed to atoms
True only in insulators
True
44.
A metal has a band gap of about 5 eV. True or false?
False, because metals have no band gap (bands overlap or are partly filled)
True
True only for copper
False, because metals have a band gap of about 1 eV
45.
An intrinsic semiconductor contains equal numbers of free electrons and holes. True or false?
False, because it contains only electrons
True
False, because it contains more holes than electrons
True only when it is doped with boron
46.
A student claims that n-type silicon carries an overall negative charge because it has extra electrons. True or false?
True
True only at high temperature
False, because each donor atom also has an extra proton, so the crystal is neutral
False, because n-type silicon is positively charged
47.
An electrician uses 1.5 m of cable whose copper core has area 2.0 x 10^-7 m^2. The core resistance is about 0.128 ohm. True or false?
False, it is about 128 ohm
False, it is about 2.3e-15 ohm
True
True only if the cable is hot
48.
A thin doped film strip, 5.0 cm long with 4.0 mm^2 cross-section, has a resistance of 250 ohm, so its resistivity is 2.0 x 10^-2 ohm m. True or false?
False, it is 3.1 x 10^6 ohm m
True
False, it is 5.0 x 10^-5 ohm m
True only for metals
49.
In a semiconductor the total current is the sum of the electron current and the hole current. True or false?
False, because holes carry no current
False, because the two currents cancel
True
True only in n-type material
50.
Adding one phosphorus atom per million silicon atoms makes only a negligible change to conductivity. True or false?
True
True only for boron
False, because it makes silicon an insulator
False, because even this tiny amount supplies many more free electrons than thermal excitation does
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