1. ENGG 1015 Tutorial
Introduction to Electrical and Electronic
Engineering – 2011 Fall Semester
Time and Venue
Class A: 1300-1355 MB201
Class B: 1130-1225 CYC-C
Tutor
Leon LEI (me): CYC806, engg1015-staff@eee.hku.hk
Tutorial materials
http://www.eee.hku.hk/~culei/ENGG1015.html
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2. ENGG 1015 Tutorial
Each class: 40 min. tutorial + 15 min. Q/A
Allow “no/low” voice discussion
Go outside for phone conversations
Same contents for Class A and Class B
Tutorial materials
Regular tutorials
Revision tutorial before examination (Tentatively)
Question bank
Solutions and Exemplars of last year homework
Extra MCQs, Extra SQs
No homework plagiarism
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3. ENGG 1015 Tutorial
Formats of tutorial materials
Slides
Handout
Problem sets
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4. ENGG 1015 Tutorial
Facebook page
“ENGG1015 FA11”
Class news, photos, videos
RSS feed
“Like”!
RSS feed
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5. ENGG 1015 Tutorial
Circuits (I)
(Class A) 12 Sept and (Class B) 6 Sept
Learning Objectives
Identify basic electrical components (Voltage,
Current, Resistance) and electrical rules
News
Lab/Project preparation
Ack.: MIT OCW 6.01 and 8.02
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6. What is a Circuit?
Circuits are connects of components
Through which currents flow
Across which voltages develop
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7. Rules Governing Flow
Rule 1: Currents flow in loops
The same amount of current flows into the bulb (top
path) and out of the bulb (bottom path)
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8. Rules Governing Flow
Rule 2: Like the flow of water, the flow of electrical
current (charged particles) is incompressible
Node
Kirchoff’s Current Law (KCL): the sum of the
currents into a node is zero
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9. Rules Governing Voltages
Voltages accumulate in loops
Kirchoff’s Voltage Law (KVL): the sum of the
voltages around a closed loop is zero
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10. Parallel Connection and Series Connection
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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11. Electrical Symbols
Voltage source
Resistor
Switch
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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12. Power Supply
http://ocw.mit.edu/courses/physics/8-02-
electricity-and-magnetism-spring-2002/video-
lectures/lecture-10-batteries-and-emf/ or
http://www.youtube.com/watch?v=RQX8I9Z
WtPQ
Definition and explanation of a battery
4:11 minutes (0:00 - 4:11)
Symbol for a battery in a circuit diagram
Definition of internal resistance
3:34 minutes (7:16 - 10:50)
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13. Measuring Voltage
A voltmeter must be hooked in parallel
across the element you want to measure the
voltage across
Voltmeters have a very large
resistance
They don’t affect the circuit
too much
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14. Measuring Current
An ammeter must be hooked in series with
the element you want to measure the current
through
Ammeters have a very low
resistance
They don’t affect the circuit
too much
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15. Resistors and Ohm’s Law
Length
Cross-section
area
Series connection Parallel connection 15

16. Resistance of Wires
Wires are made from conductors
that have resistance
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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17. Measuring Resistance
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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18. Internal Resistance
When battery delivers current to circuit, there
is a flow of current in the battery itself.
The chemical reaction will dissipate energy
Battery goes hot Lost energy in the
circuit
Equivalent to having a
resistant r inside the battery
Maximum current the battery can generate:
Imax=V/r
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19. Demonstration: Batteries in Series
http://ocw.mit.edu/courses/physics/8-02-
electricity-and-magnetism-spring-2002/video-
lectures/lecture-10-batteries-and-emf/ or
http://www.youtube.com/watch?v=RQX8I9Z
WtPQ
Connecting two batteries in series
4:30 minutes (10:50 - 15:20)
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20. Quick Checking
Resistors and Ohm’s Law
Ohm’s Law is XXX
Measure Voltage & Current
An ammeter must be hooked in XXX
Internal Resistance of Battery
Equivalent circuit of a non-ideal battery is XXX
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21. Quick Checking
Resistors and Ohm’s Law
Ohm’s Law is “V=IR”
Measure Voltage & Current
An ammeter must be hooked in series
Internal Resistance of Battery
Equivalent circuit of a non-ideal battery is
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