^Geographic meridian
^Geographic meridian
Geographic meridian at a point P on earth’s surface is a vertical plane passing through the longitude circle & axis of rotation of the earth.
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^Magnetic elements of earth
Magnetic elements of earth
Declination (θ), Dip (δ) & Horizontal component (BH) are called magnetic elements of earth as earth’s magnetic field can be completely defined in both magnitude & direction by knowing these three.
^Geomagnetism
Geomagnetism
1. Study of magnetic field of earth is called Geomagnetism or terrestrial magnetism.
2. William Gilbert (in about 1600) was the first to demonstrate that the entire earth behaves as an enormous magnet.
3. The magnitude & direction of Earth’s magnetic field can be obtained approximately by assuming that the earth has a magnetic dipole of dipole moment about 8 x 1022 J/T located at its centre tilted 11.5O from the spin axis of the earth as shown in the diagram.
4. The average strength of the earth’s magnetic field is about half a Gauss. Also Bequator = 30 μT, Bpole = 60 μT. Range of magnetic field is about 5 R from the radius of earth.
5. Earth’s mag. field changes both in magnitude & direction with the time. It is fairly constant over a span of few years but noticeable changes occur in say 10 yrs.
^Motional emf
Motional emf
No motional emf will be produced across the conductor if any two vectors 
are parallel to each other.
Polarity of the emf can be checked knowing the direction of drift of electrons using 
.
^Biot–savart’s law
Biot–savart’s law
The magnitude of the magnetic field produced depends upon
- strength of current flowing in the conductor
- shape, size of conductor &
- position of observation point where the field is to be calculated.
Direction of magnetic field due to both straight as well as curved conductor can be calculated by right hand stretched thumb rule. For straight conductor thumb point current & curl of fingers point magnetic lines while in a curved conductor reverse of it. On reversing the direction of current the direction of magnetic field produced is reversed.
^What is a vector
Description of motion along a straight line the role of direction is played by +ve & -ve signs of that direction, however to describe motion in 2 & 3 dimensions we need vectors.
^What is a vector
If both magnitude and direction are required to completely described a physical quantity, then it is called a vector. A vector quantity is represented by putting on arrow above it or by bold letter e.g. it Q is vector then we represent it as 
or Q. If a quantity can have any direction it is called polar vector. If its direction is along axis (axis of rotation), then called axial vector.
^Thermoelectric effect
Thermoelectric effect
Consider an metal rod heated at one end & cooled at the other end as shown.
The electrons in the hot region are more energetic and therefore have greater velocities than those in the cold region. Consequently there is a net diffusion of electrons from the hot end towards the cold end which leaves behind positive metal ions in the hot region and accumulated electrons in the cold region. This situation prevails until the electric field developed between the positive ions in the hot region and the excess electrons in the cold regions prevents further electron motion from the hot to cold end. A voltage developed between the hot and closed ends with the hot end at positive potential at the steady state.
This effect in which a temperature gradient between two points in a material (may be a conductor or semiconductor) gives rise to a built in electric field or a voltage difference between two points. This phenomenon is called the Seebeck effect or the thermoelectric effect.
^General
^General
| QUANTITY | SYMBOL | DEFINITION/RELATION | SI UNITS | DIMENSIONS |
| Mass | M or m | Also called inertia. | kg | [M] |
| Area | A or S | Region bounded by lines or curves in 2D. | M2 | [L2] |
| Volume | V | Space bounded by lines or curves in 3d. | m3 | [L3] |
| Density | r | Mass per unit volume | kg m – 3 | [ML – 3] |
| Linear density | m | Mass per unit length | kg m – 1 | [ML – 1] |
| Surface density | s | Mass per unit area | kg m – 2 | [ML – 2] |
| Specific volume | 1/r | Volume per unit mass | kg – 1 m 3 | [M – 1 L3] |
| Number density | n | Number of particles per unit volume. | m– 3 | [L– 3] |
| Specific gravity Or relative density | SG | density of body /density of water at 4 0C | no units | no dimensions |
^Electrolytes
Electrolytes
Liquids are categorized in to three types
- 1st type which don’t conduct e.g. Pure water or distilled water, vegetable oil.
- 2nd type which conduct but don’t dissociate into ions. e.g. Mercury.
- 3rd type which dissociate into ions & conduct when electric current is passed through them. Such liquids are called electrolytes.
^Wheatstone bridge
Wheatstone bridge
It is the quadrilateral arrangement of four resistors P, Q, R & S connected to a cell & galvanometer G as shown. Here P & Q are called ratio arms, R known arm & S unknown arm.
1. If 
, then VC = VD & the bridge is said to be balanced i.e. the potential difference across the arm CD is zero, consequently no the current through the arm CD & thus arm CD can be removed. Also the position of cell & galvanometer can be interchanged.
2. If 
, then VC ≠ VD & bridge is said to be in the unbalanced state. If 
then current flows from up & if 
then current flows down.
3. Wheatstone bridge is said to be sensitive if all the four resistances are of the same order i.e. when the current in the four branches is of the same order. In this case error associated with the measurement of X is mini.
