Course notes with several worked solutions to example problems, important equations and explainations of the following topics:
- Electric and magnetic fields, and their interaction with circuits
- Analogue circuit analysis and design skills
- Operational amplifiers, their applications and limita...
Lecturer notes:
Week 2:
More definition questions in the exam this year due to closed book. Less computation.
Basics of analogue circuits and their elements
Digital circuits and logic
Introduction to Microcontrollers
Recommended textbooks:
- Alexander and Sadiku (992pp, £41)
- Storey
- Digital design - Morris Manno and Michael Ciletti
3 hours of lectures per week + labs. Total 27+24 hours (+1 hour of tutorial/workshop every week)
When emailing identify as a student: Elec 2022
Assessments:
50% coursework and 50% final exam. Coursework assessed as following:
- Online quiz (5%)
- OpAmp circuit (20%)
- Online quiz (5%)
- Digital circuit (20%)
Newtonian Physics:
- Newton's laws of motion
- Work and energy
- Force and work
- Force and pressure
- Pressure and energy
Laws of Motion:
- 1.) Bodies continue at rest or in uniform motion unless acted on by an external force
- 2.) Force Applied is equal to the rate of change of momentum
- 3.) For every action there is an equal and opposite reaction (not need in this
module)
Mass:
Mass is a property that all matter has, which can result in weight. Weight is a force. Mass
is not a force, it just results in weight if there is gravity.
Velocity:
Velocity is how fast something is going in a given direction. It is measured in
metres/second (m/s). Units are very important in engineering.
Acceleration:
Acceleration is the rate of change of the velocity. It is measured in metres/second/second
(m/s^2)
Momentum:
Momentum is the product of mass and velocity. It is measured in kilogram metres/second
(kgm/s) P=MV
P stands for momentum. Momentum is not a force.
F=dp/dt = dmt/dt = ma. F=MA
Force:
Something that act on a body that causes it to move or the be compressed (or both). If
compressed it will "want" to move. Measured in newtons.
Energy:
Energy is the capacity to do work.
Potential energy - The energy a body has by virtue of its position in space or state
Kinetic energy - The energy a body has by virtue of its speed
Work:
Work is done when transferring energy to an object. Work = Force*Distance. W=FD. Work
and energy are both measured in joules. Work is equal to energy gained.
Work needed to lift something up:
F=MG Force=Mass*Gravity
W=MGH Work=Mass*Gravity*Height
When object is dropped:
E=MGH
MGH->1/2MV^2
Flow: Volume = pr^2
Flow=Volume/Second
Pressure=Force/Area
Pressure in a fluid is not directional. It is the same in all directions. Pressure is not a force.
Scalar.
Pressure = force/cross-sectional area
Work=Pressure*Volume Moved
Lecture 2:
Circuits and Electronics (20 Credits) Page 1
,Lecture 2:
Flow is greater through wider pipes
Flow is proportional to the pressure difference
V=LA
W=FD
W=VP
W=LAp0
W=LA(p1-p0)
Power supplied by pump = (Pout-Pin)*Flow
Power dissipated by pipe = (Pin-Pout)*Flow
Power entering the circuit=(Pout-Pin)*Flow
-If negative, power is leaving the circuit
Ground:
System should be closed. "No leaks". If the circuit is not closed the charge doesn’t move therefore
no current. Ohms law only applies to closed circuits. The ground is shown as 3 lines getting
smaller. Ground has 0 voltage.
In the example:
Ground is 0 V and V=12 so the difference is 12 volts
12/0.024 = 500ohms
V=IR
24 milliamps = 0.024 amps (/100)
In real devices there is a small amount of resistance in all components, ei wires, voltmeter.
In example 2:
The currents flows from both cells towards the resistor. V=IR, R=1kohm, Va=7, Vb=2
Va-Vb=5
I=5/1000
Higher voltage in left side therefore current pushes to the left.
Krichhoffs law:
Σii=0
The current flowing into a node is equal to the current flowing out. Wires do not leak.
Circuits and Electronics (20 Credits) Page 2
,Week 3 - Laws and Resistors
09 October 2022 17:22
In terms of pipes. X+Y+Z=0 when Z flows towards the junction.
This concept can be applied to current in circuits.
This is called Kirchhoff's law. It states that the current flowing into
a junction must be equal to the current flowing out.
Ei. If 100 flows into the X side then 100 must flow out of the Z and
Y sides.
In the example:
If we guess the current from the ammeter is flowing towards
the junction then, c1+c2+c3=0
8mA+6mA+C3=0
C3=-14
The reading on the ammeter is 14mA
The minus means we were wrong in our assumption of the
direction of the current. It flows towards the Ammeter 14mA.
In the next example:
On the ammeter the red side is the positive side. When
current flows in through here the value is positive
We to find C1 to determine the current direction.
60 flows into the junction meaning that 60 must come out.
60-50=10
Therefore C1 is 10nA
Next 90+10 flows into the junction meaning 100 must flow
out.
The current flows into the ammeter from the negative side
therefore it reads -100nA
Kirchhoff's second law:
The sum of all voltage differences around the components in a
closed loop is zero.
Potential energy gained by a unit of charge going through a
potential difference of ΔV
E=ΔV
The potential energy gained by a unit of charge going around a
circuit is:
ΔV1+ ΔV2+ ΔV3… = Σ(I around loop) Δvi
V=IR
At the first resistor V=2I
At the second resistor V=I
This means V1=V2/2
Or
V2=2V1
3+3V1=0
V1=-3
Voltage flowing through a voltmeter:
The long thin line of the cell represents the positive terminal and the short side is
the negative terminal. Here we have 7 volts flowing into the black(negative) side
and 4 volts flowing into the positive side. This means the voltmeter will read -3 as
we have -7+4=-3.
In the second example we have 9+8 = 17 flowing into the negative side and 2
flowing into the positive side meaning we have 2-17 = -15. Therefore the voltmeter
reads -15v
Circuits and Electronics (20 Credits) Page 3
, we have -7+4=-3.
In the second example we have 9+8 = 17 flowing into the negative side and 2
flowing into the positive side meaning we have 2-17 = -15. Therefore the voltmeter
reads -15v
What's wrong with Ohms law?
Not all laws are exact. This difference is more dramatic in some cases.
In some resistors - ones with 6 bands - the resistance changes with temperatures.
If you left a circuit running for hours the current and would change with the
resistance making ohms law somewhat inaccurate for the value of resistance that
is known.
KVL is also flawed. (don’t worry about this for now)
KCL - When wires are long the resistance stops being negligible.
Resistors and Resistor Networks:
Simulating resistors - Will be seen later in labs
How do we find resistance between X & Y
Resistor in series:
V is the voltage difference
V=RI
V1+V2= V
V1=R1I1
V2=R2I2
V=R1I1+R2I2
I1=I2 as wires do not leak and the current doesn’t move/split.
Engineers don’t like decimal points. 3K3= 3.3K
1k+500+3k3= 1000+500+3300=4800 or 4.8k or 4k8
Example 3:
(1000*1000)/(1000+1000) = 500
Example 4:
500+1000=1500
(1500*1500)/(1500+1500) = 750
Circuits and Electronics (20 Credits) Page 4
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