ENGG 1015 Tutorial
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Introduction to Electrical and Electronic
Engineering – 2011 Fall Semester
Time and Venue
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Class A: 1300-1355 MB201
Class B: 1130-1225 CYC-C
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Tutor
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Tutorial materials
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Leon LEI (me): CYC806, engg1015-staff@eee.hku.hk
http://www.eee.hku.hk/~culei/ENGG1015.html
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ENGG 1015 Tutorial
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Each class: 40 min. tutorial + 15 min. Q/A
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Allow “no/low” voice discussion
Go outside for phone conversations
Same contents for Class A and Class B
Tutorial materials
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Regular tutorials
Revision tutorial before examination (Tentatively)
Question bank
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Solutions and Exemplars of last year homework
Extra MCQs, Extra SQs
No homework plagiarism
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ENGG 1015 Tutorial
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Formats of tutorial materials
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Slides
Handout
Problem sets
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ENGG 1015 Tutorial
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Facebook page
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“ENGG1015 FA11”
Class news, photos, videos
RSS feed
“Like”!
RSS feed
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ENGG 1015 Tutorial
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Circuits (I)
(Class A) 12 Sept and (Class B) 6 Sept
Learning Objectives
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Identify basic electrical components (Voltage,
Current, Resistance) and electrical rules
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News
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Ack.: MIT OCW 6.01 and 8.02
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Lab/Project preparation
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What is a Circuit?
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Circuits are connects of components
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Through which currents flow
Across which voltages develop
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Rules Governing Flow
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Rule 1: Currents flow in loops
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The same amount of current flows into the bulb (top
path) and out of the bulb (bottom path)
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Rules Governing Flow
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Rule 2: Like the flow of water, the flow of electrical
current (charged particles) is incompressible
Node
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Kirchoff’s Current Law (KCL): the sum of the
currents into a node is zero
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Rules Governing Voltages
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Voltages accumulate in loops
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Kirchoff’s Voltage Law (KVL): the sum of the
voltages around a closed loop is zero
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Parallel Connection and Series Connection
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Loads are connected in parallel across power supply.
When the elements are connected one after another,
so that the current passes through each element
without any branches, the elements are in series.
Parallel connection
Series connection
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Electrical Symbols
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Voltage source
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Resistor
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Switch
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Often connected in series
When the switch is open the load is disconnected
When the switch is closed, the load is connected
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Power Supply
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http://ocw.mit.edu/courses/physics/8-02electricity-and-magnetism-spring-2002/videolectures/lecture-10-batteries-and-emf/ or
http://www.youtube.com/watch?v=RQX8I9Z
WtPQ
Definition and explanation of a battery
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Symbol for a battery in a circuit diagram
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4:11 minutes (0:00 - 4:11)
Definition of internal resistance
3:34 minutes (7:16 - 10:50)
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Measuring Voltage
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A voltmeter must be hooked in parallel
across the element you want to measure the
voltage across
Voltmeters have a very large
resistance
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They don’t affect the circuit
too much
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Measuring Current
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An ammeter must be hooked in series with
the element you want to measure the current
through
Ammeters have a very low
resistance
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They don’t affect the circuit
too much
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Resistors and Ohm’s Law
Length
Cross-section
area
Series connection
Parallel connection
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Resistance of Wires
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Wires are made from conductors
that have resistance
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Include a series resistor to
model the wire resistance Rw
The current into a resistor is given by
I= V/Req = V/(R+Rw1+Rw2)
In practice, we will make the wire resistance much
smaller than the component resistance: R >> Rw
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Measuring Resistance
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An ohmmeter must be hooked in parallel
across the element you want to measure the
resistance
Ohmmeters apply a voltage and measure the
current that flows
They typically won’t work
if the resistor is powered
(connected to a battery)
Measuring R1
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Internal Resistance
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When battery delivers current to circuit, there
is a flow of current in the battery itself.
The chemical reaction will dissipate energy
Æ Battery goes hot Æ Lost energy in the
circuit
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Equivalent to having a
resistant r inside the battery
Maximum current the battery can generate:
Imax=V/r
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Demonstration: Batteries in Series
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http://ocw.mit.edu/courses/physics/8-02electricity-and-magnetism-spring-2002/videolectures/lecture-10-batteries-and-emf/ or
http://www.youtube.com/watch?v=RQX8I9Z
WtPQ
Connecting two batteries in series
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4:30 minutes (10:50 - 15:20)
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Quick Checking
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Resistors and Ohm’s Law
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Measure Voltage & Current
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Ohm’s Law is XXX
An ammeter must be hooked in XXX
Internal Resistance of Battery
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Equivalent circuit of a non-ideal battery is XXX
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Quick Checking
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Resistors and Ohm’s Law
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Ohm’s Law is “V=IR”
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Measure Voltage & Current
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Internal Resistance of Battery
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An ammeter must be hooked in series
Equivalent circuit of a non-ideal battery is
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