Moving charges in Electric and Magnetic fields Magnetic flux: The total number of magnetic field lines of force passing through a closed surface are called magnetic flux It is denoted by Φ B Unit: weber Intensity of the magnetic field ( H ): Intensity of the magnetic field at a point in a magnetic field is the force experienced by one unit north pole paced at that point . Unit: A/m Magnetic induction or Magnetic flux density ( B ): The number of magnetic field lines of force passing through a unit area is called magnetic induction or magnetic flux density. Magnetic induction B = Φ B /A Unit: weber/ m 2 or tesla or gauss (in CGS) Force on a charged particle in an electric field According to the Intensity of electric field definition, the intensity of the electric field ( E ) at a point in an electric field is the force experienced by a unit positive charge (q) placed at that point.
Hydrogen is in abundance around the sun but not around earth. Why? ANSWER: The escape velocity on the sun is very high compared to that on the earth. The gravitational pull of the sun is very large because of its larger mass compared to that of the earth. So it is very difficult for hydrogen to escape from the sun's atmosphere because r.m.s velocity of hydrogen is more than escape velocity(11.2 km/sec). But on the sun r.m.s velocity of the hydrogen is less than the escape velocity of the sun. Hence hydrogen is abundant on sun. Note: r.m.s velocity means root mean square velocity) escape velocity of the planet/star is the minimum velocity required to a body to escape form the planet/star.