medan magnet
-
Upload
dwi-maryanti-putri -
Category
Documents
-
view
10 -
download
0
description
Transcript of medan magnet
MEASURED MAGNETIC FIELD of EARTH by ROTATING COILS
Dwi Maryanti Putri* , Meili Yanti , Nurul Muthmainnah Herman
Laboratorium Fisika Modern Jurusan Fisika FMIPA
Universitas Negeri Makassar
Abstract. Have performed experiments on measuring magnetic field of earth by rotating coils The purpose
of this lab is to determine the components of Earth's magnetic field and determine the angle of inclination of the
earth's magnetic field . The magnetic field is the area immediately surrounding the magnet is still affected by the
magnet. Inclination angle is the angle formed by the Earth's magnetic field with the Earth's rotation axis. Data
collected by the scientific method which in this experiment determine how Large component of the magnetic field
obtained in the direction of the x-axis rotation of 0,002711 tesla. Direction of the y-axis rotation of 0,002436 tesla
and direction of z-axis 0,000838 tesla The angle of inclination of the Earth's magnetic field direction obtained at
12,95 o. Besed on the data obtained it can be concluded that the value of each axis of the magnetic field observed
in the different.
KEYWORDS: magnetic field, inclination angle, Earth Magnets.
INTROCUCTION
One of the defense mechanisms of the
earth of radiation attacks and the waste of space
is the presence of Earth's magnetic field. The
Earth's magnetic field to form two magnetic
poles. North pole of the earth magnetic field
contained in the geographic south pole of the
Earth while the Earth's magnetic field south pole
is at the north pole of the earth. However, no
precise compass facing north because there are
differences in the geography of the earth lies the
northern axis of the earth with the axis of the
magnetic south pole. The angle formed by the
irregularities of the earth's magnetic field with
the geographical direction of the earth is also
called the angle of inclination.
The existence of Earth's magnetic field
is used by humans in terms that facilitate human
navigation in determining direction. Magnetic
field whose origin is still not fully understood by
scientists, capable of capturing particles of high
energy nuclear, generally in the form of protons
and electrons.
Research shows irregularities of the
earth's magnetic field due to the mineral
constituent is no magnetic rocks such as
Magnetite (Fe3O4), Hematite (Fe2O3), ilmenite
(FeTiO3) and Pyrrhotit (Fe2-XS). The atoms in
a mineral are arranged geometrically in which
the individual and the range of the electron orbit
is directed through a certain small zone a few
microns in diameter and are known as magnetic
domains, causing the magnetic minerals. The
power of magnetism depends on the proportion
of the range of the electrons in the same direction
or reverse each other. Magnetite and pyrrhotit
have strong magnetism because the electrons in
the same direction, while hematite and ilmenite
strength is weak because of the surrounding
electrons tend to reverse direction. At
temperatures above the Curie temperature /
critical temperature (55oC-600oC) motions of
atoms are so large that there is no magnetic
domeinnya and the resulting properties of
magnetism is lost. When the temperature drops
below the critical temperature, the direction is
set again by the influence of the earth's magnetic
field.
THEORI
Scientists are of the opinion that the
magnetic field generated by an electric current
due to the iron-nickel core of the planet, and the
current generated due to the rotation of the
planet. This explanation is nothing more than a
theory that it can not explain why the planet
Jupiter which has a nickel-iron core at most, and
in the interior may consist of metallic hydrogen,
also has a magnetic field. Then the core of the
Sun is made up of super-hot plasma composed
mostly of hydrogen and helium, also has a
magnetic field. [1]
In 1830 to 1842, Karl Frederick Gauss
conduct detailed observations of the Earth's
magnetic field. He concluded that the source of
Earth's magnetic field comes from the earth. He
also stated that the Earth's magnetic field also
has a close relationship with the rotation of the
earth because the earth's magnetic poles close to
the Earth's spin axis. In addition to the Earth's
magnetic field axis move around a lot. In the
history of the earth has happened a few times
where the earth's north pole reversal becomes
south and south becomes north. Since 160
million years ago has happened hundreds of
times a magnetic pole reversal. Although it has
happened hundreds of times, this magnetic pole
reversal does not show a specific pattern of
repetition so it is difficult to predict when the
magnetic poles will reverse again. [1]
In 1927, Jacob Clay serorang Dutch
scientists have found evidence that the primary
cosmic radiation influenced by the Earth's
magnetic field. In air travel to Indonesia, he
found that the intensity of cosmic radiation is
reduced when approaching the equator of the
Earth's magnetic field. Earth's magnetic field
emanating from the earth extends to far into
space. The magnetic field forming an invisible
shield called the magnetosphere. This shield
protects us from cosmic radiation and the
enormity of the dangers that come from the sun.
These hazards include storm the sun (in the form
of a continuous stream of electrically charged
particles), the explosion of the Sun (which is
within a few minutes can release energy
equivalent to billions of hydrogen bombs), and
coronal mass hurling / Coronal Mass Ejections.
Regional Earth's magnetic field that traps
particles high-speed nuclear particles form a belt
that was first discovered by a team of American
scientists led by James S. van Allen. James Van
Allen continued his research even successful
shows a radiation belt around the Earth. The
radiation belts last named Van Allen radiation
belts.
The lines of magnetic force of the earth
that extends far into space, capturing charged
particles moving encircling lines of magnetic
force. Because these lines are most common in
polar regions, then in this region of electrically
charged particles to penetrate into Earth's
atmosphere and causing a nature show called
polar light or aurora.
Review a induction coil with winding
number N and the cross-sectional area ๐ด = ๐๐ 2.
When the coil is rotated with angular velocity ฯ
in a uniform magnetic field B, the diameter d, as
the coil axis, then the resulting magnetic flux ฮฆ
by:
ฮฆ = ๐๐ 2๐๐ต cos(๐๐ก) (1)
By using the time of revolution T = 2ฯ/ฯ iinduksi
peak value of AC is given by
๐ =2๐๐๐ 2
๐๐ต = ๐๐ต (2)
with
๐ =2๐๐๐ 2
๐ (3)
When the coil is directed to the rotation axis z,
the amplitude of the voltage is given by
๐๐ง = ๐โ๐ต๐ฅ2 + ๐ต๐ฆ2 (4)
This value is induced into the earth's magnetic
field;
๏ฟฝโ๏ฟฝ = (
๐ต๐ฅ
๐ต๐ฆ
๐ต๐ง
) (5)
For reasons of symmetry, beraku on;
๐๐ฅ = ๐โ๐ต๐ง2 + ๐ต๐ฆ2 (6)
๐๐ง = ๐โ๐ต๐ง2 + ๐ต๐ฆ2 (7)
Furthermore, by using equation (5), (6) and (7)
obtained the components of the earth's magnetic
field;
๐ต๐ฅ = โโ๐๐ฅ2+๐๐ฆ2+๐๐ง2
2๐2 (8)
๐ต๐ฆ = โ๐๐ฅ2โ๐๐ฆ2+๐๐ง2
2๐2 (9)
๐ต๐ง = โ๐๐ฅ2+๐๐ฆ2โ๐๐ง2
2๐2 (10)
The angle of the direction of Earth's magnetic
field is obtained โ
of the equation;
Tan๐ =๐ต๐ง
โ๐ต๐ฅ2+๐ต๐ฆ2=โ
๐๐ฅ2+๐๐ฆ2+๐๐ง2
2๐๐ง2 (11)
The above equation is mathematically correct,
the value of the root is likely to be negative when
the measurements were carried out around the
equator. [2]
EXPERIMENTAL METHODOLOGY
The experiments were done using a tool
components as follows: A pair of Helmholtz
coils, sensors Cassy, MV_box, Cassy Lab,
connecting cable โ 2.5 mm 2, 200 cm red and
blue, the experimental motors, control units for
motors and experimental PC with Windows
2000 to above.
The first thing that is done in this
experiment is to ensure that all components of
the equipment has been installed as shown
below:
FIGURE 1. Composition of the experimental
apparatus.
The next step is to connect all components
of a device to a voltage source PLN including
computers. Then Cassy clicking the icon on the
computer, after which it will appear cassy menu.
Then set the voltage range between -1 mV-
measurement 1mV and 20 second time limit.
Turning on the motor, then increase the speed
slowly approaching 0.3 rev / s. Set 2 connecting
cables red and blue to be wrapped around the
motor experiment and ensure the cable does not
come to the end. Furthermore, experimental data
recording the induced voltage as a function of
time by pressing F9 on the keyboard or select the
measurement on the menu Cassy.
For each data recording is completed, the
data storage process is done by selecting Save on
the File menu. The recording process is carried
out five times for each dimension, where data
recording is done in three-dimensional space, x,
y, and z.
EXPERIMENTAL RESULTS AND DATA
ANALYSIS
Magnetic field measurements performed using a
Helmholtz coil with the following sizes:
Number of turns (N) : 320
Diameter : 13,5 x 10-2 m
The radius (R) : 6,75 x 10-2 m
Plot the results of the data obtained in the
measurement of the voltage in the direction of
rotation of the x, y, and z.
GRAPH 1. Relationship between Period (T)
with voltage (V) in the X axis
GRAPH 2. Relationship between Period (T)
with voltage (V) in the Y axis
-0,4
-0,2
0
0,2
0,4
0 5 10 15 20
Vo
ltag
e (
mV
)
Period (s)
-0,4
-0,2
0
0,2
0,4
0 5 10 15 20
Vo
ltag
e (
mV
)
Period (s)
GRAPH 3. Relationship between Period (T)
with voltage (V) in the Z axis
Data Analysis
N = 320
R = 0,0675 m
On the X axis
V1 = 0,331 mV
V2 = 0,321 mV
V3 = 0,317 mV
V4 = 0,306 mV
Vx= ๐1+ ๐2+ ๐3+ ๐4
4
= (0,331+0,321+ 0,317+0,306) ๐๐
4
= 0,318 mV
T1 = 2,2 s
T2 = 4,4 s
Tx= T2 โ T1
= ( 4,4 โ 2,2 ) s
= 2,2 s
On the Y axis
V1 = 0,344 mV
V2 = 0,342 mV
V3 = 0,346 mV
V4 = 0,344 mV
Vy= ๐1+ ๐2+ ๐3+ ๐4
4
= (0,344+0,342+ 0,346+0,344) ๐๐
4
= 0,344 mV
T1 = 1,3 s
T2 = 3,6 s
Ty= T2 โ T1
= ( 3,6 โ 1,3 ) s
= 2,3 s
On the Z axis
V1 = 0,418 mV
V2 = 0,409 mV
V3 = 0,401 mV
V4 = 0,428 mV
Vz= ๐1+ ๐2+ ๐3+ ๐4
4
= (0,418+0,409+ 0,401+0,428) ๐๐
4
= 0,414 mV
T1 = 1,9 s
T2 = 4,3 s
Tz= T2 โ T1
= ( 4,3 โ 1,9 ) s
= 2,4 s
So the Earth's magnetic field strength on the X
axis
Bx = โโ ๐๐ฅ
2 + ๐๐ฆ2 + ๐๐ง
2
2๐2
with
a = 2 ๐ ๐๐ 2
๐
= 2 (3,14)(320)(0,0675 ๐)2
2,2 ๐
= 2 (3,14)(320) (4,56 ๐ฅ 10โ3 ๐2)
2,2 ๐
= 4,165 ๐2
๐
then
Bx = โโ (0,318 ๐๐)2 + (0,344 ๐๐)2 + (0,414๐๐)2
2 (4,165 ๐2
๐ )2
= 0,002711 Tesla
-0,5
0
0,5
0 5 10 15 20
Vo
lta
ge
(mV
)
Period (s)
Earth's magnetic field strength on the Y
By = โ๐๐ฅ
2โ ๐๐ฆ2 + ๐๐ง
2
2๐2
with
a = 2 ๐ ๐๐ 2
๐
= 2 (3,14)(320)(0,0675 ๐)2
2,3 ๐
= 2 (3,14)(320) (4,56 ๐ฅ 10โ3 ๐2)
2,3 ๐
= 3,984 ๐2
๐
then
By = โ (0,318 ๐๐)2โ (0,344 ๐๐)2 + (0,414 ๐๐)2
2(3,984 ๐2
๐ )2
= 0,002436 Tesla
Earth's magnetic field strength on the Z
Bz = โ ๐๐ฅ
2 + ๐๐ฆ2 โ ๐๐ง
2
2๐2
with
a = 2 ๐ ๐๐ 2
๐
= 2 (3,14)(320)(0,0675 ๐)2
2,4 ๐
= 2 (3,14)(320) (4,56 ๐ฅ 10โ3 ๐2)
2,4 ๐
= 3,818 ๐2
๐
then
Bz = โ (0,318 ๐๐)2+ (0,344 ๐๐)2 โ (0,414 ๐๐)2
2(3,818 ๐2
๐ )2
= 0,000838 Tesla
So, the total value of the Earth's magnetic field
is:
BT = โ๐ต๐ฅ2 + ๐ต๐ฆ
2 + ๐ต๐ง2
= โ(0,000007349 + 0,000005934 + 0,0000007022)๐๐๐ ๐๐
= โ0,00001398 ๐๐๐ ๐๐
= 0,003739 Tesla
The angle of the direction of Earth's magnetic
field is obtained โ
Tan ๐ = ๐ต๐ง
โ๐ต๐ฅ2+ ๐ต๐ฆ
2
= 0,000838
โ(0,002711)2+(0,002436)2
= 0,000838
โ0,000007349 + 0,000005934
= 0,000838
0,003644
= 0,229
๐ = arc tan 0,188
= 12,95 o
DISCUSSION
In this activity we perform measurements
of Earth's magnetic field with rotating coils.
Rotating coil in question is a Helmholtz coil is a
coil that can ignore the Earth's magnetic field
where his fingers as large as the distance
between the two coils. There are three axis
directions are analyzed, namely the direction of
the x, y, and z. The analysis is intended to
analyze in determining the value of the magnetic
field and the magnitude of the angle of
inclination earthโs generated. Large component
of the magnetic field obtained in the direction of
the x-axis rotation of 0,002711 tesla. Direction
of the y-axis rotation of 0,002436 tesla and
direction of z-axis 0,000838 tesla The angle of
inclination of the Earth's magnetic field direction
obtained at 12,95 o.
CONCLUSION
Based on the results of experimental data,
a large component of the magnetic field obtained
different in each direction of the axis of rotation
(x, y, and z). Large component of the magnetic
field obtained in the direction of the x-axis
rotation of 0,002711 tesla. Direction of the y-
axis rotation of 0,002436 tesla and direction of
z-axis 0,000838 tesla The angle of inclination of
the Earth's magnetic field direction obtained at
12,95 o.
REFERENCES
[1]Mukhlis Akhadi dan Hasnel Sofyan, 1999.
Medan Magnet Bumi. Buletin ALARA. Jakarta
[2]Subaer, dkk. 2014. Penuntun Praktikum
Eksperimen Fisika I Unit Laboratorium Fisika
Modern Jurusan Fisika FMIPA UNM