2nd Hour Agenda
Teaming
Batteries
Introduction to Ohms Law
EGR 101
1
Collaborative Learning
• Positive Interdependence
– Share responsibilities (sink or swim together)
– Be sure that all team members learn the
material
• Your success is linked to the success of your
teammates
– Involve each team member
• Each team member’s efforts are required for
success
• No “free riders”
EGR 101
2
Code of Collaboration
• Every team member is responsible for the
team’s progress and success!
–
–
–
–
–
–
Attend all classes and team meetings
Be on time
Come prepared
Carry out assignments on schedule
Be an active listener
Listen to and show respect for the contributions of the
other team members
• Constructively criticize ideas, not people
• Resolve conflicts and avoid disruptive behavior
EGR 101
3
Code of Collaboration
• Avoid disruptive side conversations
– Only one person speaks at a time
• Everyone participates, no one dominates
• Be brief and to the point
– Avoid long anecdotes and examples
• Set a norm for behavior
– “Code of Conduct” for your team
EGR 101
4
Out-of-Class Team Activity
• Work together to develop your own team’s
Code of Conduct
– What do you expect of each other?
Make your expectations explicit (like attending
all meetings, arriving on time, prepared, etc)
– What are the consequences if someone fails
to meet expectations?
• Due at the beginning of class next
Tuesday
EGR 101
5
Where Does Current Come
From?
• The free electrons in a conductor need to
be replaced when they move through the
conducting medium (the wire).
• These electrons are replaced by electrons
from a source of energy such as a battery.
EGR 101
6
Circuit Components
• Batteries
+
+
EGR 101
7
Source of Voltage in a Battery
• A chemical reaction within the battery
separates positive and negative ions
(charged atoms)
• When the battery is connected to a circuit,
the negative charge move toward the
positive charge and a current is produced
• The amount of current is constrained by
the resistance of the circuit
EGR 101
8
Example of A Battery
The source of energy E in (Joules) releases charges Q in
(Coulombs)
Voltage (V) – the difference in potential that uses E = one
Joule (J) of energy to move a charge Q = one coulomb (C).
EGR 101
9
Current Direction
We will adopt “Conventional Flow” for all of our work!
EGR 101
10
Mathematical Relation
• E: Energy required to move charges in
Joules (J).
• Q: Charge value in Coulombs (C).
• V: Voltage or potential difference across
the battery's posts in volts (V).
•
Thus, V = E / Q.
• In units: 1 Volt = 1 Joule/Coulomb
EGR 101
11
Team In-class Activity (15 minutes)
• A 10 V source uses 2 Joules of energy per
second. Calculate the current being used
by the source.
• Hint, turn the word problem into equations;
write down what you know.
EGR 101
12
When batteries are
connected with their
polarities in the same
direction, they are in a
series-aiding
arrangement.
EGR 101
13
When batteries are
connected with their
polarities in the
opposite direction,
they are in a
series-opposing
arrangement.
EGR 101
14
In Class Activity
• What is the total voltage between
terminals A and B in the figure below?
A
B
9V
4V
15V
Which terminal is at a higher potential?
EGR 101
15
Introduction to Ohm’s Law
• A 1 Ohm resistance limits the current to
1 Amp when 1 Volt is applied.
V = I.R
EGR 101
16
Ohm’s Law
V  IR
• Three forms:
• Use the form that best
describes the quantity
that you are trying to
determine
EGR 101
V
I 
R
V
R 
I
17
Determine the Current
I
+
_
V
I 
R
EGR 101
18
Determine the Voltage
+
_
V  IR 
EGR 101
19
Determine the Resistance
+
_
V
R 
I
EGR 101
20