Chapter 4: Moving Charges and Magnetism
NCERT Class 12 Physics, Part I, Chapter 4. 9 lessons, 18 narrated 3D videos, 9 simulations and 18 quiz questions, following the textbook section by section.
- Magnetic force and the Lorentz forceIn 1820, Hans Christian Oersted noticed something strange. A compass needle kept near a wire swung round whenever a current was switched on in the wire.
- Motion in a magnetic fieldFire a proton into a uniform magnetic field, at right angles to the field. Here the field points into the screen, shown by the crosses.
- The Biot–Savart lawEvery current-carrying wire, whatever its shape, can be cut into tiny straight pieces. Each piece, of length dl and carrying current I, is called a current element,…
- Field of a circular current loopTake a circular loop of radius R carrying a steady current I. Let us find the magnetic field at a point P on its axis, a distance x from the centre.
- Ampere’s circuital law and the solenoidDraw any closed loop in space. Walk round it in small steps dl. At each step, multiply the step by the part of B along it, B·dl, and add them all up round the loop.
- Force between parallel currentsTwo long straight wires, a and b, run parallel to each other, a distance d apart. Wire a carries a current I a, and wire b carries I b, in the same direction.
- Torque on a current loopHang a rectangular loop of wire, carrying a current I, in a uniform magnetic field B. Its sides have lengths a and b. What does the field do to it?
- The moving coil galvanometerA moving coil galvanometer detects and measures small currents. Inside it is a coil of many turns, free to turn about a fixed axis, between the poles of a strong magnet.
- Velocity selector and the cyclotronThis is an extra topic. It is beyond the current NCERT syllabus, but it is useful for competitive exams, and it puts the Lorentz force to work.