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प्रश्न
Write any two important points of similarities and differences each between Coulomb's law for the electrostatic field and Biot-Savart's law of the magnetic field ?
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उत्तर
Following are the similarities between Coloumb's law for the electrostatic field and Biot-Savart's law of the magnetic field:
(i) Both the laws obey superposition principle.
(ii) In both the laws, the field at any point varies inversely to the square of distance from source to the point of observation. Hence, both the laws are long range.
Following are the differences between Coloumb's law for the electrostatic field and Biot-Savart's law for the magnetic field:
| Coloumb's Law for Electrostatic Field | Biot-Savart's Law for Magnetic Field |
| 1. The electrostatic field is produced by the electric charge, q, which is a scalar quantity. | The magnetic field is produced by the current element,
|
| 2. The electrostatic force acts along the line joining the source and the point, which is the displacement vector. | The magnetic field acts perpendicular to the plane containing current element
\[I {dl}^\rightharpoonup\] and displacement vector \[r^\rightharpoonup\] which is along the direction of \[(I {dl}^\rightharpoonup \times r^\rightharpoonup )\].
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F = `(Qq)/r^2 hatr`
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The number [3] actually arises from the speed of light in vaccum which is now taken to be exactly given by c = 2.99792458 × 108 m/s. An approximate value of c then is c = [3] × 108 m/s.
(i) Show that the coloumb law in cgs units yields
1 esu of charge = 1 (dyne)1/2 cm.
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