Download PowerPoint – Elec L9 – V I Graphs

ELECTRICITY
VOLTAGE CURRENT GRAPHS
B
Attention
Grade
A
Lesson time (mins)
D
E
Stress
How much energy I have
Revision time (hours)
Jan Feb Mar Apr May Jun
Your love of Science
What conclusions can make from the information given
below?
C
No. of Science lessons
F
Axes not
labelled so no
relationship
shown
Jan Feb Mar Apr May Jun
B
Attention
Grade
A
Revision time (hours)
Lesson time (mins)
Your love of Science
Why do we use graphs? What’s the point?
C
No. of Science lessons
To visualise information to help identify trends and relationships.
Graph A – As revision time goes up, grade goes up.
Graph B – As lesson time increases, pupil attention decreases.
Graph C – The more science lessons you have, there is no change in your love of Science.
THESE GRAPHS ARE JUST FOR EXAMPLES, I KNOW YOU LOVE SCIENCE MORE
AND MORE AS I TEACH IT!
RELATIONSHIPS DISPLAYED ON GRAPHS
What general trends do these graphs show?
Positive correlation
Negative correlation
No correlation
As A increase, B increase
As A increases, B
decreases
No relationship, data
spread
GRAPH VOCABULARLY
UP
RISE, INCREASE, GROW
DOWN
FALL, DEACREASE,DROP, DECLINE
NO CHANGE
CONSTANT.STABLE, STAY THE
SAME
FREQUENT CHANGE
FLUCTUATE, VARY
AT THE TOP
PEAK, HIGHEST POINT/VALUE
AT THE BOTTOM
LOW/LOWEST POINT
DATA ANALYSIS
You should have data for each different component (filament bulb,
diode and fixed resistor).
Using this data you now need to draw a graph for each
component. Plot current against voltage to produce and I-V
characteristic graph
Our axes look like
this
I
Use a ruler!
V
I–V GRAPH FOR A FILAMENT BULB
I
V
The resistance of a bulb increases as the temperature of the metal
Discuss the trend of the graph and try to describe it in
filament increases. The ions in the metal vibrate more as temperature
your book and
explain
become constant
increases.
Thiswhy
resistscurrent
the flowmay
electrons.
RESISTANCE OF AN RESISTOR
I
V
Ohm’s law
The
current
resistorand
at a constant
temperature
Discuss
theflowing
trendthrough
of theagraph
try to describe
it inis
directly proportional to
the potential
your
book. difference across it.
I-V GRAPH FOR A DIODE
Explain the trend of the graph for a diode.
(What does a diode do?)
A diode only lets current flow in one direction
I
V
In the forward direction the line curves towards the current axis, the current is able to flow
but isn’t directly proportional to potential difference.
In backwards direction the resistance is very high so current cannot flow so the line is flat.
CURRENT-VOLTAGE GRAPHS SUMMARY
I
I
Bulb
V
Resistor
V
I
V
Diode
You need to be able to recognise each of these
THERMISTOR
A thermistor is a component which changes resistance due to temperature.
As the temperature increases a thermistors resistance decreases.
Resistance (Ω)
What might a
thermistor be useful
for?
Temperature (oC)
Draw a general graph trend to show how resistance of a thermistor will change
as the temperature increases.
LDR – LIGHT DEPENDENT RESISTOR
An LDR is a component which changes its resistance due to intensity of light.
As the light intensity increases an LDRs resistance decreases.
Resistance (Ω)
What might an LDR
be useful for?
Light intensity (Lux)
Draw a general graph trend to show how resistance of an LDR will change as the
light intensity increases.