The Transformer and
Power Transmission
An ideal transformer consists of two coils wound on the same iron core. An alternating voltage V1 is
applied to the primary coil, and the output voltage V2 is across the
resistor of resistance R.
a step-up transformer
step-down transformer
The Transformer and
Power Transmission
The primary winding in this transformer is directly attached to the prongs of the plug. The secondary winding is connected to the power cord on the right, which runs to an electronic device. Many of these power-supply transformers also convert alternating current to direct current.
Circuit diagram for a transformer.
Rectifiers and Filters
The process of converting alternating current to direct current is called rectification, and the converting device is called a rectifier.
(a)A half-wave rectifier with an optional filter capacitor.
(b)Current versus time in the resistor. The solid curve represents the current with no filter capacitor, and the dashed curve is the current when the circuit includes the capacitor.
The RC circuit in Figure (a) is one example of a filter circuit, which is used to smooth out or eliminate a time-varying signal.
After rectification, the voltage still contains a small AC component at 60 Hz (sometimes called ripple), which must be filtered.
Rectifiers and Filters
(a) A simple RC high-pass filter. (b) Ratio of output voltage to input voltage for an RC high-pass filter as a function of the angular frequency of the AC source.
Rectifiers and Filters
(a) A simple RC low-pass filter. (b) Ratio of output voltage to input voltage for an RC low- pass filter as a function of the angular frequency of the AC source.
Maxwell’s Equations and Hertz’s
Discoveries
Plane
Electromagnetic Waves
Waves, in which the electric and magnetic fields are restricted to being parallel to a pair of perpendicular axes, are said to be linearly polarized waves.
This entire collection of waves is often called a plane wave. A surface connecting points of equal phase on all waves which we call a wave front is a geometric plane.
A surface connecting points of equal phase for this situation is a sphere, so this is called a spherical wave.
Plane
Electromagnetic Waves
Plane
Electromagnetic Waves
That is, at every instant the ratio of the magnitude of the electric field to the magnitude of the magnetic field in an electromagnetic wave equals the speed of light.
Electromagnetic Waves