VII. Прочитайте текст о типах электрических цепей без словаря

А fundamental part of circuit analysis is determining whether the matter has a return path to the power source. If the matter is blocked from returning to the power source, either wholly or partially, the entire assemblage will be prevented from accomplishing work. In an electrical circuit, an open circuit is caused intentionally when a user opens a switch or unintentionally when vibration or mechanical damage severs a wire. In a pneumatic or hydraulic circuit, this occurs when a valve is closed or there is a leak in one of the lines or components.

In electrical circuits, closing a switch creates a closed loop for the electrons to flow through. This is sometimes referred to as "completing the circuit." Other synonyms are also used.

In an electrical or electronic circuit, sometimes an unintended connection is made, such as when insulation is broken, frayed, melted or chewed by rodents, or a technician inserts a metal tool into a live device. When this happens, current bypasses some or all of the components in the circuit, taking a "shorter" path back to the power source. This can lead to excessive current drain, which in turn generates excessive heat, damaging or destroying sensitive parts of the system such as transistors and ICs.

In electronics,components of an electronic circuit can be connected in series or in parallel. Components connected in series are connected along a single path, so the same current flows through all of the components. Components connected in parallel are connected such that there are multiple independent paths along which the current can flow; in other words, the current is split among the different paths. A circuit composed solely of components connected in series is known as a series circuit; likewise, one connected completely in parallel is known as a parallel circuit.

VIII. Расскажите о разнице между

A) closed circuits and open circuits

B) series and parallel circuits

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Circuit theory

An electrical network or electrical circuit is an interconnection of analog electrical elements such as resistors, inductors, capacitors, diodes, switches and transistors. It can be as small as an integrated circuit on a silicon chip, or as large as an electricity distribution network.
A circuit is a network that has a closed loop i.e. a return path. A network is a connection of 2 or more simple circuit elements, and may not be a circuit.

The goal when designing electrical networks for signal processing is to apply a predefined operation on potential differences (measured in volts) or currents (measured in amperes). Typical functions for these electrical networks are amplification, oscillation and analog linear algorithmic operations such as addition, subtraction, multiplication, division, differentiation and integration.

In the case of power distribution networks, engineers design the circuit to transport the energy as efficiently as possible while at the same time taking into account economic factors, network safety and redundancy. These networks use components such as power lines, cables, circuit breakers, switches and transformers.

To design any electrical circuits, electrical engineers need to be able to predict the voltages and currents in the circuit. Linear circuits can be analysed to a certain extent by hand because complex number theory gives engineers the ability to treat all linear elements using a single mathematical representation.

A number of electrical laws apply to all electrical networks. These include:

Kirchhoff's current law: the sum of all currents entering a node is equal to the sum of all currents leaving the node.

Kirchhoff's voltage law: the directed sum of the electrical potential differences around a circuit must be zero.

Ohm's law: the voltage across a resistor is the product of its resistance and the current flowing through it.

the Y-delta transform

Norton's theorem: any two-terminal collection of voltage sources and resistors is electrically equivalent to an ideal current source in parallel with a single resistor.

Thevenin's theorem: any two-terminal combination of voltage sources and resistors is electrically equivalent to a single voltage source in series with a single resistor.

Millman's method: the voltage on the ends of branches in parallel is equal to the sum of the currents flowing in every branch divided by the total equivalent conductance.

Other more complex laws may be needed if the network contains nonlinear or reactive components. Non_linear self_regenerative hetrodyning systems can be approximated. Applying these laws results in a set of simultaneous equations that can be solved either by hand or by a computer.

When faced with a new circuit, the software first tries to find a steady state solution. This is a solution where all nodes conform to Kirchhoff's Current Law and the voltages across and through each element of the circuit conform to the voltage/current equations governing that element.

Once the steady state solution is found, the operating points of each element in the circuit are known. For a small signal analysis, every non-linear element can be linearized around its operation point to obtain the small-signal estimate of the voltages and currents. This is an application of Ohm's Law. The resulting linear circuit matrix can be solved with Gauss-Jordan elimination.

Lesson 4