28.Applications of step-up and step-down transformers

A step-up transformer is one whose secondary voltage is greater than its primary voltage. This kind of transformer "steps up" the voltage applied to it. For instance, a step up transformer is needed to use a 220v product in a country with a 110v supply. Its the opposite of the above, and would be used to run for example a 110v product in a country with a 220v mains supply. . A transformer is made from two or more coils of insulated wire wound around a core made of iron. When voltage is applied to one coil (frequently called the primary or input) it magnetizes the iron core, which induces a voltage in the other coil, (frequently called the secondary or output). The turns ratio of the two sets of windings determines the amount of voltage transformation.An example of this would be: 100 turns on the primary and 50 turns on the secondary, a ratio of 2 to 1.

29. Maximum Power Transfer in AC Circuits. the maximum power transfer theorem states that, to obtain maximum external power from a source with a finite internal resistance, the resistance of the load must be equal to the resistance of the source as viewed from the output terminals. The theorem results in maximum power transfer, and not maximum efficiency. If the resistance of the load is made larger than the resistance of the source, then efficiency is higher, since a higher percentage of the source power is transferred to the load, but the magnitude of the load power is lower since the total circuit resistance goes up.If the load resistance is smaller than the source resistance, then most of the power ends up being dissipated in the source, and although the total power dissipated is higher, due to a lower total resistance, it turns out that the amount dissipated in the load is reduced.

30. Power balance in AC Circuits. For record of balance of power in a complex aspect, we observe in the beginning a branch : i.e . record considers at once active and jet powers of a user. For our instance the balance of power registers:

Or .

31. . Phasor Diagrams. Impedance and Reactance

A phasor is a vector that contains both magnitude and direction or amplitude and phase information. It can be used to represent AC quantities. Since phasors have magnitudes and directions, they can be represented as complex numbers. A phasor notation or phasor domain is a method that uses complex numbers to represent the sinusoidal quantities for analysing AC circuits.

Impedance is the total measure of opposition to electric current and is the complex (vector) sum of (“real”) resistance and (“imaginary”) reactance.

Electrical reactance, the opposition to alternating current due to capacitance (capacitive reactance) or inductance (inductive reactance)

32. . Superposition. To linear chains we apply method of superposition when the initial circuit design breaks into the subcircuits containing on one source taking into account internal resistances others, i.e. short-circuits there where there were EMF sources become ( ) where there were current sources ruptures ( ) become . Resultants currents in the initial circuit design are defined by algebraic summation (superposition) of currents of branches of subcircuits.

.

For nonlinear circuits MN unacceptably.

33. Resonance in Parallel RLC Circuit