Ch 10Magnetic Fields due to Electric Current — Class 12 Physics, concept-first.

Class XI's study of magnetism began with the bar magnet as a given object -- something with a fixed North and South pole whose field could be measured and drawn.

The two-wire demonstration of Section 10.1 shows that a current-carrying wire experiences a force when placed in the magnetic field produced by a neighbouring current-carrying wire.

A key structural consequence of Section 10.2 is that the magnetic force on a moving charge is always perpendicular to its velocity, and always has a constant magnitude for a fixed speed and field stre…

Particle accelerators -- machines that use electric and/or magnetic fields to bring charged particles up to very high energies (from a few MeV to several GeV) -- are essential tools both for fundament…

Sections 10.2 and 10.3 assumed the charged particle's entire velocity lies in a plane PERPENDICULAR to the magnetic field , producing pure circular motion.

Sections 10.2 through 10.4 dealt with the magnetic force on a SINGLE moving charge. But an electric current in a wire is, physically, an enormous number of individual charge carriers (conduction elect…

Consider a straight wire of length (Fig. 10.8), carrying a steady current , placed in an external magnetic field applied perpendicular to the wire.

The straight-wire result of Section 10.5.1, , applies directly only when the current-carrying conductor is itself perfectly straight.

Section 10.5.2 established that, for a wire of arbitrary shape in a UNIFORM magnetic field, the total force depends only on the vector displacement between the wire's two endpoints.

Section 10.6 showed that a current loop in a UNIFORM magnetic field experiences zero net force, but can still experience a net TORQUE, since different segments of the loop experience forces acting alo…

A direct and historically important practical application of the torque formula (Section 10.7) is the moving coil galvanometer -- an instrument for measuring small electric currents (or, with an appro…

Section 10.7 derived the torque on a current-carrying coil in the compact form . This particular combination of quantities, , recurs so often, and plays such a central organising role, that it is give…

Section 10.8 established a direct structural analogy between a magnetic dipole's torque, , and an electric dipole's torque, (from Class XI). That same analogy extends naturally to POTENTIAL ENERGY.

Sections 10.1 through 10.9 dealt entirely with the FIRST half of this chapter's subject: given a magnetic field, what force (and torque) does it exert on a moving charge or a current? The remaining se…

As the first, and most basic, application of the Biot-Savart law, consider a long straight wire carrying current , and a point P at perpendicular distance from the wire (Fig. 10.16).

The two-wire demonstration that opened this chapter (Fig. 10.1, Section 10.1) showed QUALITATIVELY that current-carrying wires exert forces on one another -- attractive for parallel currents, repulsiv…

Having worked out the field of a straight wire (Section 10.10.1), the next natural shape to consider is a CIRCULAR arc of wire -- and, as a special case, a complete circular loop, which turns out to b…

Section 10.12 found the field only at the CENTRE of a circular current loop. This section generalises that result to any point P on the loop's AXIS -- the straight line through the centre of the loop,…

Building directly on the on-axis field formula of Section 10.13, this section examines the overall SHAPE of the magnetic field lines produced by a circular current loop, and shows that -- viewed from…

The Biot-Savart law (Section 10.10) is completely general -- it can, in principle, be used to find the magnetic field of ANY current distribution, however complicated -- but, as the sometimes-lengthy…

Having established Ampere's law and demonstrated its power on the simplest possible case (a single long straight wire, Section 10.15), this section turns to two more elaborate, but practically very im…

Consider a long, closely-wound helical coil of conducting wire -- a SOLENOID -- with its diameter assumed much smaller than its length (Fig. 10.24).

A TOROID can be thought of as a solenoid of finite length, bent around and joined into a closed, hollow, ring- or tube-shaped structure -- similar in overall shape to a pressurised inner tube inside a…

Sample papers and previous-year board questions for this subject.