Sections A, B, C, and D.

The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor. It is measured in Ohms and the relation between resistance (R), current (I) and electrical potential (V) is Ohm's law: V = IR. Ohm's law says that a larger voltage makes more current flow if resistance is fixed. Or if resistance is lower at the same voltage, more current will flow.

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In this section we study the magnetic field of either a permanent magnet or the field produced by a flow of current in a coil. Field is measured in Gauss. The compass, magnet and coil are all draggable. The earth's magnetic field can also be demonstrated.

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In this section we study electric and magnetic fields with different orientations to see their effects on neutral, positive and negative charges. For the electric field case the particles have zero initial velocity. In second case with a magnetic field in the x-direction the initial velocity is zero but there is a check-box so that you can give the particles an initial velocity in the +x direction. In the third case the magnetic field is rotated so that it points into the screen.

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If a changing magnetic field is present near a wire that is part of a circuit it will cause current to flow in the circuit. This is known as Faraday's law and is the basis for a lot of modern technology. Electric generators, metal detectors, the read head on a computer hard drive, credit card readers, cassette tape readers.   We will see several applications for sound reproduction.

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Sections A, B, C, D, and E.

It is not possible to record, transmit and replay sounds perfectly so that they sound exactly as they were heard originally. This chapter explains several electronic devices used in sound recording and reproduction using concepts that were introduced in previous chapters.

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