Physcs 2
Physcs 2
Physcs 2
SCHOOL
SESSION : 2019 – 20
Roll No:
CERTIFICATE
This is to certify that PARV KHANDELWAL of class XII has
successfully completed the research on the topic " To study the earth's
magnetic field using a compass needle” under the guidance of Mrs.
SHAILJA PANDEY during the year 2022-202. Based on the curriculum
issued by the CBSE and has given a satisfactory account of it in the
project
Principal
ACKNOWLEDGEMENT
I feel proud to present my project in physics on the topic “To study the
earth's magnetic field using a compass needle”. This project wouldn’t
have been completed without the proper guidance of my physics teacher
MRS. SHAILJA PANDEY, who guided me throughout this project in
every possible way. The project involves various difficult lab experiments
which have to be carried out by the student to obtain the observations and
conclude the report on a meaningful note. Thereby I would like to thank
MRS. SHAILJA PANDEY for guiding me on step by step basic and
ensuring that I completed all my experiments with ease.
PARV KHANDELWAL
Class XII
INDEX
S.No Topic
1 Aim
2 Materials Required
3 Introduction
4 Theory
5 Procedure
8 Precautions
9 Bibliography
AIM
The aim of the project is to study the Earth’s magnetic field and find its
value (BH) using a tangent galvanometer.
Tangent galvanometer
The North and South magnetic poles wander widely, but sufficiently
slowly for ordinary compasses to remain useful for navigation. However,
at irregular intervals averaging several hundred thousand years, the Earth's
field reverses and the North and South Magnetic Poles relatively abruptly
switch places. These reversals of the geomagnetic poles leave a record in
rocks that are of value to paleomagnetists in calculating geomagnetic
fields in the past. Such information in turn is helpful in studying the
motions of continents and ocean floors in the process of plate tectonics.
The magnetosphere is the region above the ionosphere and extends several
tens of thousands of kilometers into space, protecting the Earth from the
charged particles of the solar wind and cosmic rays that would otherwise
strip away the upper atmosphere, including the ozone layer that protects
the Earth from harmful ultraviolet radiation.
Earth's magnetic field serves to deflect most of the solar wind, whose
charged particles would otherwise strip away the ozone layer that protects
the Earth from harmful ultraviolet radiation. One stripping mechanism is
for gas to be caught in bubbles of magnetic field, which are ripped off by
solar winds.
The intensity of the field is often measured in gauss (G), but is generally
reported in nanoteslas (nT), with 1 G = 100,000 nT. A nanotesla is also
referred to as a gamma (γ). The tesla is the SI unit of the Magnetic field,
B.
The field ranges between approximately 25,000 and 65,000 nT (0.25–0.65
G).
Near the surface of the Earth, its magnetic field can be closely
approximated by the field of a magnetic dipole positioned at the center of
the Earth and tilted at an angle of about 10° with respect to the rotational
axis of the Earth. The dipole is roughly equivalent to a powerful bar
magnet, with its South Pole pointing towards the geomagnetic North Pole.
The north pole of a magnet is so defined because, if allowed to rotate
freely, it points roughly northward (in the geographic sense). Since the
north pole of a magnet attracts the south poles of other magnets and repels
the north poles, it must be attracted to the South Pole.
TANGENT GALVANOMETER
Principle
The tangent galvanometer works on the principle of tangent law.
The tangent law of magnetism states that the tangent of the angle of
a compass needle which is due to the movement under the influence
of magnetic field is directly proportional to the ratio of strengths of
two perpendicular magnetic fields.
In simpler words, the tangent of the angle made by the moving
needle under the magnetic field directly indicates the strength of the
perpendicular magnetic fields.
Definition
Tangent galvanometer is the device which was used to measure
small amounts of electric current.
Construction
Working
Hence the compass needle responds to the vector sum of the two
fields.
This deflection angle is equal to the tangent of the ratio of those two
fields.
APPLICATIONS
Plug Key
THEORY
Eq 1: F = H tan θ
Eq 2 : 𝐹 = μ0 2πIN
4π R
Eq 3 : 𝐻 = 2π×10−7IN
𝑅𝑡𝑎𝑛𝜃
Eq 4: 𝑡𝑎𝑛𝜃 𝐼 = 𝜇0 2𝜋𝑁
4𝜋 RH
Connections are made as shown in the figure given below, where K is the
key, E the battery, A the ammeter, R the rheostat, C the commutator, and
T.G the tangent galvanometer. The commutator can reverse the current
through the T.G coil without changing the current in the rest of the circuit.
Taking the average of the resulting two readings for deflection averages
out, any small error in positioning the T.G coil relative to the earth’s
magnetic field H.
CIRCUIT DIAGRAM
2. Using spirit level, level the base and the compass needle in compass
box of tangent galvanometer by adjusting the leveling screw.
3. Now rotate the coil of the galvanometer about its vertical axis, till the
magnetic needle, its image in the plane mirror fixed at the base of the
compass box and the coil, i.e. All
5. In this setting, the ends of the aluminum pointer should read zero-zero.
If this is not so, rotate the box without disturbing the position of the coil
till at least one of the ends of the pointer stands at the zero marks.
6. By closing the key K, the current flow in the galvanometer. Read the
both ends of the pointer. Now reverse the direction of current by using the
reversing key. When the mean values of both deflections shown by the
pointer in the two cases (i.e., before and after reversing the current) differ
by more than 1o, then turn slightly the vertical coil until the two values
agree. This will set the plane of the coil exactly in the magnetic meridian.
10. By changing the value of current, take four or more set of readings and
plot the graph between I and tan𝜃. The graph will be a straight line.
11. Measure the inner and the outer diameter of the coil with a half meter
scale at least three times.
OBSERVATIONS AND CALCULATIONS
θ1 θ2 θ3 θ4 Obs Corrected
1. 35 35 35 35 35 0.70 0.15 0.15
2. 49 47 60 64 53.6 1.36 0.20 0.20
3. 36 36 55 58 46.25 1.04 0.25 0.25
4. 50 50 65 68 58.2 1.61 0.30 0.30
5. 45 45 64 65 53.8 1.37 0.27 0.27
Table 2. For radius of tangent Galvanometer
m = tanθ
I
Now substitute the m in Eq. (4),
m = μ0 2πN
4π RH
RESULT