Robert Cinca - Physics
400
surge current time against 1/(final steady current) 2
surge current time
1/(final
steady current) 2
using against
the excel
model
using the excel model
line of best fit: Δt = (7.3 ± 2.1) I -2 + (15 ± 37)
line of best fit: Δt = (7.3 ± 2.1) I -2 + (15 ± 37)
400
350
350
300
300
250 maximum gradient line: Δt = 9.9 I -2 - 34
250
200 maximum gradient line: Δt = 9.9 I -2 - 34
200
150
minimum gradient line: Δt = 5.7 I -2 + 40
150
100
minimum gradient line: Δt = 5.7 I -2 + 40
100
50
50
0
0 0
0
10
10
20
30
current) 2 , I -2 /A -2
20 1/(final steady 30
1/(final steady
40 50 60
40 50 60
current) 2 , I -2 /A -2
Figure 16: Excel Model Graph
Figure 16: Excel Model Graph
My model had similarities with my experimental results but also some differences.
My model had similarities with my experimental results but also some differences.
They were similar, in that:
They were similar, in that:
The model showed a surge current.
showed up a with
surge
The model ended
a current.
reasonable temperature for a filament bulb 11
11
The
model
ended was
up with
reasonable
temperature
for a in
filament
bulb
(when
the model
used a to
get the normal
final current
the 6.5V
0.30A
(when the
model
was used
to get the normal
final current in the 6.5V 0.30A
filament
bulb,
I recorded
a temperature
of 2850K±50K).
filament bulb, I recorded a temperature of 2850K±50K).
They were different, in that:
They were different, in that:
The excel model reached the final current sooner than the experiment (the
surge
The excel
model
reached
final current
than
the experiment
current
times
for my the
experiment
are sooner
larger by
a factor
of three). (the
current
times
for my experiment
are larger
by a rather
factor than
of three).
surge
The model
had
an instantaneous
maximum
current,
a short delay
as
The seen
model
had experiment.
an instantaneous maximum current, rather than a short delay
in my
as seen in my experiment.
The possible reason for this difference is that in the model self-inductance of the
12
The
possible
reason
this difference
is that in the force
model
self-inductance
of the
(e.m.f.)
was not included.
filament,
which
would for
create
a back electromotive
12
(e.m.f.) volume
was not on
included.
filament, reason
which would
create
a back electromotive
Another
could be
the possible
expansion of force
the filament’s
heating.
Another
reason
the the
possible
expansion area
of the
filament’s
volume
on heating.
I have taken
the could
length be and
cross-sectional
of the
filament
as constant,
with
I have
taken the length
and expansion.
the cross-sectional
area
filament
as constant,
with
no
consideration
of volume
Tungsten
has of a the
volume
expansion
coefficient
no consideration of volume expansion. Tungsten has a volume expansion coefficient
11
“Types of Lighting: Incandescent Bulbs”, The Pennsylvania State University [Online][Date Accessed
11
20/07/13]
https://www.e-education.psu.edu/egee102/node/2035
(The Pennsylvania
State
“Types of URL:
Lighting:
Incandescent Bulbs”, The Pennsylvania State University
[Online][Date
Accessed
University) URL: https://www.e-education.psu.edu/egee102/node/2035 (The Pennsylvania State
20/07/13]
University)
th
12
“Self-Inductance”, A Level Physics, 4 Edition (Muncaster, 1993), p658
12
th
“Self-Inductance”, A Level Physics, 4 Edition (Muncaster,
1993), p658
40
22