Department of Physics
Module PH1 - EL
Electronics
Dr Stephen Sweeney
Room 21DJ02
[email protected]
Lecture 1
1
We live in an age of electronics
From toasters to mobile phones we
exploit electronics in every aspect of
our lives.
As physicists we are interested in
understanding the principles they
depend on and using them as tools.
Lecture 1
2
1
X-ray detector
Electronic devices are
the physicist’s senses.
Virtually all our measurements are
recorded as electronic signals.
We need to understand how to deal
with these.
Lecture 1
3
The Delphi vertex detector at CERN
• Thousands of
detectors
• Millions of
electronic
components
• Hundreds of
physicists and
engineers across
Europe
Lecture 1
4
2
Physics can contribute to the
continuing development of electronics
• Pushing the limits of speed and complexity
• New materials
• New physical principles
Lecture 1
5
Things you will NOT learn on this course
• You will NOT learn how to design practical
electronic circuits.
• You will NOT learn how to repair your TV
or change a fuse.
• You will NOT learn how to design a power
distribution network.
This is engineering …
Lecture 1
6
3
Things you WILL learn on this course
• You will learn the principles of electronic networks.
• You will learn how to simplify complex networks
and circuits to predict their properties.
• You will learn how to
interpret electronic
measurements.
• You will learn how to think
of electronic effects in terms
of fundamental physics
Lecture 1
7
How are we going to do this?
• Lectures
• Problem Sheets and and Tutorials
• Individual and Group Study and Revision
• Above all, if you don’t understand something ASK!
⇒ Deal with in tutorials (most things in physics are best
understood through examples)
⇒ Get together as a group – help each other
⇒ If you are still stuck – e-mail me to arrange a meeting
Lecture 1
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4
How are we going to assess you?
“An unexamined life is not worth living”
Socrates (~400 BC)
• Computer based and marked assignments (30%
of total) [weeks 10 & 15]
• Examination next summer (70% of total)
Lecture 1
9
What will we cover?
D.C. Circuit Theory: Electrical nomenclature, current, voltage, resistance,
conductance, power and decibels. Kirchhoff's laws. Current and voltage sources,
Thévenin and Norton sources. Condition for maximum power transfer. Analysis
of simple networks of resistors.
A.C. Circuit Theory: Capacitors and Inductors. Energy storage. Use of
complex numbers. Concepts of reactive impedance and frequency dependence.
Transient response. Tuned circuit principles (ωo, Δω and Q). Concept of link
between frequency and transient responses.
Systems and Circuits: Concept of feedback, operational amplifiers, frequency
response of circuits with reactive components, filters, Bode plots. Active filters,
differentiators, integrators. Oscillators.
Lecture 1
10
5
Reading Material
Most of what we will discuss is covered at some level by most
textbooks on General Physics or Electricity. Some books that cover
this course are:
• “Electronics: Circuits, Amplifiers and Gates”, D.V. Bugg, Hilger (1991)
• “Fundamentals of Electric Circuits, C.K. Alexander and M.N.O. Sadiku,
McGraw Hill (2003).
• “Introduction to Electric Circuits”, R.C. Dorf, Wiley (1989).
• “Introductory Linear Circuits and Electronics”, M.C. Kelley and B.
Nichols, Wiley (1988).
Go to the library and find a book(s) that YOU are comfortable with
Lecture 1
11
A diversion about numbers and units
Lecture 1
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6
Numbers: 1.00000
In physics we often have to deal with very large and
very small numbers
• 299792458
(velocity of light in metres per second)
• 0.00000000000000000000000000166056 (mass of
proton in kilogram)
• 6022045000000000000000000 (atoms in 1 mole of
substance)
Lecture 1
13
Numbers: 2.0000 x 100
Exponent notation
– Express each number as a number between 1 and 10
multiplied by a power of 10
• 2.99792458 x 108 m s-1 (velocity of light)
(mass of proton)
• 1.66056 x 10-27 kg
• 6.022045 x 1023 mol-1 (atoms in 1 mole of substance)
mantissa
exponent
This is usually called scientific notation on calculators
“E notation” on computers: 1.66056E-27, 6.022045E23
Lecture 1
14
7
Numbers: 3 x 100
Rounding
– Don’t write numbers with more significant figures than is
necessary especially in experimental work (we will be
working to 2 or three significant figures at most)
– Use the rounding rules (round up if the number you are
losing is 5 or higher)
• 3.00 x 108 ms-1
• 1.66 x 10-27 kg
• 6.02 x 1023
(velocity of light)
(mass of proton)
(atoms in 1 mole of substance)
Lecture 1
15
Numbers: 1.6 x 101 x 2.5 x 10-1
Multiplying numbers in exponent form:
– MULTIPLY the mantissas and ADD the exponents:
– If necessary adjust the exponent to keep the mantissa between 1
and 10
• E.g. mass of 1 mole of protons:
= 1.66 x 10-27 x 6.02 x 1023 kilogram
= (1.66 x 6.02) x 10 ( -27 + 23)
= 9.9932 x 10-4
= 10 x 10-4
= 1.0 x 10-3 kilogram (or 1 gram)
Lecture 1
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8
Numbers
Dividing numbers in exponent form:
– DIVIDE the mantissas and SUBTRACT the exponents (top –
bottom)
– Adjust exponent to keep mantissa between 1 and 10
• E.g. time for light to travel 10 km (1.0 x 104 m)
= 1x104 / 3x108 seconds
= (1/3) x 10 ( 4 -8)
= 0.33 x 10-4
= 3.3 x 10-5 seconds
Lecture 1
17
Units
• All measurable physical quantities have a UNIT
–
–
–
–
–
400 metres
3 x 108 metres per second
24 hours
1 kilogram
6.02 x 1023 mol-1
• Most units are derived from a small number of
fundamental units or DIMENSIONS
–
–
–
–
Length [L]
Mass
[M]
Time
[T]
a few others (e.g. temperature)
• e.g. Velocity is metres per second, [L][T]-1
Lecture 1
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9
SI Units
• The Système International des Unités defines the
fundamental dimensions as METRE, KILOGRAM and
SECOND (M.K.S.)
– All other units are derived from these (and a few others)
• The names and SYMBOLS for the derived units are
defined by the SI convention. e.g.
–
–
–
–
metre, m;
second, s;
newton (force = mass x acceleration = kg m s-2), N
Pa
pascal (pressure = force / area = kg m-1 s-2),
• Other units (inches, pounds, yards, miles, etc.) should not
be used in any scientific work
Lecture 1
19
SI prefixes
The SI convention defines multiplying prefixes to
indicate multiple or fractional values of units
Increasing…
Decreasing…
Name
symbol
multiplier
Name
symbol
multiplier
kilo
k
103
milli
m
10-3
mega
M
106
micro
μ
10-6
giga
G
109
nano
n
10-9
tera
T
1012
pico
p
10-12
peta
P
1015
femto
f
10-15
ALL other prefixes (e.g. centimetres, dekagrammes, decilitres, hectares) are
unofficial and should NOT be used in scientific writing
Lecture 1
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10
SI rules for writing quantities
• Use the correct SI unit for the quantity measured
• Choose the multiplier prefix so that the number is
between 1 and 1000
• Use “.” (full stop, point or dot) for the decimal point
• Leave one space between the number and the unit
• Optionally break up long fraction parts in groups of
three digits
– i.e. 299.792 458 Mm s-1
Lecture 1
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Examples
Measured value
5000metres
5 hours
0.01 cm
350 dekagram
0.000005 s
3 x 108 m s-1
91300000 Hz
Correct SI notation
5.000 km
18.000 ks (not common!)
100 μm
3.50 kg
5 μs
300 Mm s-1
91.3 MHz
Lecture 1
22
11
Doing calculations with prefixes
1. Convert all the prefixed quantities to
exponent form
2. Carry out the calculation
3. Convert the result back to SI notation
Lecture 1
23
Example
• The impedance of a capacitor C [units = farads (F)]
at a frequency f [units = hertz (Hz)] is given by
1
Z=
ohms
2π fC
• When f = 1 MHz and C = 10 pF
1
1. Z =
ohms
6
2π ×10 × 10 × 10−12
1
= 15900 ohms
2. Z =
6.28 × 10−5
3. Z = 15.9 kΩ
Lecture 1
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12
Problems
1. The printout from your data processing program shows the following values.
Express these in standard S.I. format with an accuracy of 3 significant figures.
0.501567E+02 VOLTS
0.126748E-05 SECOND
9.976307E+00 AMPS
7.325718E+13 METRE
5.381792E-04 COULOMB
1.167830E+10 HERTZ
0.968245E+05 OHMS
4.234901E-05 KILOGRAM
2. Evaluate the following expressions in two ways: (i) by estimation: evaluate the
mantissa expression and the exponent expression separately and write down an
approximate answer WITHOUT using a calculator, (ii) use a calculator
1.57x1012 x 9.5x10-3 / 3.45x10-7
3.56x10-23 / (4.24x10-6 + 7.5x10-7)
2.22x1016 / 34.5x1017
Lecture 1
25
13