First of all magnetic field lines are produced from magnetic pole and ends on it. These lines form closed loop. Charge moving in magnetic field experiences force which is dependent of velocity of charged particle. Its direction will be perpendicular to both of magnetic field and velocity. That particle will follow circular or helical path based on angle between velocity and magnetic field. Also current carrying wire placed in magnetic field experience force. Remember expression for both of above. Cyclotron is accelerator device based on above concept.
Biot-Savart’s law tells about magnetic field due to current element at given point which is dependent of distance of point, current and angle. But calculating magnetic field is difficult from this law so Ampere law makes it easy. It’s similar to Gauss’s law in electrostatics. Solenoid and toroid behaves like magnet if current is passed through them.
Using above law, we can compute magnetic field inside them. Also, there will be force between two current carrying wires due to their magnetic fields. Parallel currents will attract where anti parallel will repel each other. There exist magnetic dipole like electric one, consisting of north and south-pole. Current carrying loop will experience torque in between magnetic dipoles. It’s better to know to calculate magnetic dipole moment of electrons.
Galvanometer is application of above concept. Also know about how galvanometer is converted to ammeter and voltmeter by adding shunt resistor in parallel and series respectively and their calculations. Study properties of magnetic materials. When magnet of magnetic dipole moment, m is placed in uniform magnetic field, it’ll not experience force but torque and it’ll have potential energy. Along this earth’s magnetic field has two components. Know about them and terms like declination and dip angles.
In magnetic properties, it’s important to know about magnetization, magnetic intensity, permeability, susceptibility and their relation with magnetic field. There are various magnetic materials like diamagnetism, para-magnetism and ferromagnetism. Know about their behavior, Curie temperature and hysteresis loop also.
Mistakes/challenges-
- While using right hand thumb rule, see type of charge. Learn that rule perfectly,Many things depend on it.
- Don’t confuse in magnetic properties. There are many interdependent terms so understand them conveniently.
- Don’t mistake in theory questions on magnetic materials. Actually they are scoring questions.
- Pay attention to vector quantities and directions, also see at what angles their values are maximum.
Tips/guidelines-
- This chapter is analogous to electrostatics. Replacing electric terms with magnetic ones, you’ll see similar concepts. So, it’ll be easier.
- Don’t ignore applications like cyclotron, galvanometer. Understand them.
- Sometimes electric field is introduced in problems, then apply electrostatics’ concepts. Practice those problems.
- Remember basic expressions of magnetic field like due to current carrying loop on its axis.
- Practice problems on converting galvanometer into ammeter and voltmeter.
- Remember relations between magnetic properties.
This topic contains concepts similar to electrostatics. Focus on Ampere law, right hand thumb rule, magnetic properties and applications. And above all practice.
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