Optics
Physics
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AC Circuits
7-23-99
Alternating current
Direct current (DC) circuits involve current flowing in one direction.
In alternating current (AC) circuits, instead of a constant voltage
supplied by a battery, the voltage oscillates in a sine wave pattern,
varying with time as:
In a household circuit, the frequency is 60 Hz. The angular frequency is related to the frequency, f, by:
Generators, Inductance, and Transformers
Applications of electromagnetic induction
7-22-99
Electromagnetic induction is an incredibly useful phenomenon with a wide variety of applications. Induction is used in power generation and power transmission, and it's worth taking a look at how that's done. There are other effects with some interesting applications to consider, too, such as eddy currents.
Faraday's Law
Induced EMF
7-21-99
Linking electricity and magnetism
So far we've dealt with electricity and magnetism as separate topics.
From now on we'll investigate the inter-connection between the two,
starting with the concept of induced EMF. This involves generating a
voltage by changing the magnetic field that passes through a coil of
wire.
Electromagnetic Induction and AC Circuits
Ferromagnetism
Magnetic materials
7-20-99
Ferromagnets
A ferromagnetic material is one that has magnetic properties similar to those of iron. In other words, you can make a magnet out of it. Some other ferromagnetic materials are nickel, cobalt, and alnico, an aluminum-nickel-cobalt alloy.
Forces and Torques; Examples
Forces on currents in magnetic fields
7-15-99
The magnetic force on a current-carrying wire
A magnetic field will exert a force on a single moving charge, so it follows that it will also exert a force on a current, which is a collection of moving charges.
The force experienced by a wire of length l carrying a current I in a magnetic field B is given by
The Magnetic Field; The Force on a Charged Particle
Magnetic fields and how to make them
7-14-99
Magnetism
There is a strong connection between electricity and magnetism. With electricity, there are positive and negative charges. With magnetism, there are north and south poles. Similar to charges, like magnetic poles repel each other, while unlike poles attract.
Magnetism
Kirchoff's Laws and Multi-loop Circuits
Multi-loop Circuits and Kirchoff's Rules
Before talking about what a multi-loop circuit is, it is helpful to define two terms, junction and branch.
A junction is a point where at least three circuit paths meet.
A branch is a path connecting two junctions.
In the circuit below, there are two junctions, labeled a and b. There are three branches: these are the three paths from a to b.
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