Module test

Electrical engineering and electronics basics

213 group Oleg Sirko

Current

Electric current refers to the flow of electric charge through a specific point in a circuit over a given
period of time. It is quantified in amperes (A), where 1 ampere equals 1 coulomb per second. Electric
current can be classified into direct current (DC) and alternating current (AC).

Example: In a basic circuit containing a light bulb, the electric current represents the movement of
charge that illuminates the bulb.

Voltage

Voltage, also known as electric potential, is the difference in electric potential energy between two
points in a circuit. This difference creates an electric field that causes electrons to move. It is measured
in volts (V) and indicates how strongly electrons are pushed through a conductor.

Example: In Ukraine, the standard voltage in household outlets is 220 V. This potential difference
enables the operation of household appliances like refrigerators and televisions.

Resistance

Resistance is a property of a material that opposes the flow of electric current. It is measured in ohms
(Ω) and is influenced by the material's type, length, and cross-sectional area.

Example: A resistor with a value of 100 Ω in an electric circuit serves to limit the current, thereby
safeguarding other components from potential damage due to overload.

In the depicted circuit, resistors R1R_1 and R2R_2 are connected in parallel. By using a voltmeter and
ammeter, one can measure voltage and current, then apply Ohm’s Law to calculate either the resistance
of individual resistors or the total equivalent resistance of the parallel configuration.

R=UIR = \frac{U}{I}

Where:

 RR – resistance (Ω)
 UU – voltage (V)
 II – current (A)

Conductance

Conductance represents a material’s capacity to transmit electric current. It is the reciprocal of

resistance and is measured in siemens per meter (S/m). Materials with high conductance are commonly
used in electrical wiring and electronic components.
Example: Copper and aluminum are widely used for wiring due to their excellent conductive
properties. For instance, copper has a conductance of approximately 58×10658 \times 10^6 S/m,
making it an optimal choice for efficient electrical transmission.

Although the illustration aligns partially with the text by showing copper and aluminum wires, it
should also emphasize the importance of insulating materials, which are essential for preventing
current leakage. Other materials like silver and gold, known for their superior conductivity, are also
employed in advanced electronic and industrial applications.

1. Active Power (P)

Active power refers to the actual energy consumed by resistive elements in an electrical circuit. This is
the portion of power that performs useful work, such as generating heat or motion, and is measured in
watts (W).

In purely resistive circuits, the voltage and current are in phase, meaning their waveforms align
perfectly. As a result, all the electrical energy is efficiently converted into usable work, with no energy
being stored or returned to the source.

Formula:

P=UI⋅cos⁡(φ)P = UI \cdot \cos(\varphi)

Where:

 PP — active power (W)

 UU — voltage (V)
 II — current (A)
 φ\varphi — phase angle between voltage and current

In a circuit with only resistive components, the phase angle φ=0∘\varphi = 0^\circ, so cos⁡(0)=1\cos(0)
= 1, and the formula simplifies to:

P=U⋅IP = U \cdot I

This corresponds with Ohm's Law for AC resistive circuits, where there is no reactive component,
and all supplied energy is utilized effectively.
2. Reactive Power (Q)

Reactive power is the portion of electrical energy that alternates back and forth between the source
and the reactive components of a circuit, such as capacitors and inductors. Unlike active power, it
does not perform useful work, but it is essential for maintaining voltage stability in alternating
current (AC) systems.

It is measured in volt-amperes reactive (VAR).

In capacitive circuits, reactive power is temporarily stored in the electric field between the plates and
is then returned to the source during the AC cycle. No net energy is consumed, but this exchange is
vital for the correct functioning of voltage-dependent equipment.

Formula:

Q=UI⋅sin⁡(φ)Q = UI \cdot \sin(\varphi)

Where:

 QQ — reactive power (VAR)

 UU — root mean square (RMS) voltage (V)
 II — RMS current (A)
 φ\varphi — phase angle between current and voltage

In a purely capacitive circuit, the current leads the voltage by 90°, making the cosine of the phase
angle zero (cos⁡(90°)=0)(\cos(90°) = 0), so active power P=0P = 0 while reactive power Q≠0Q \ne 0.

Although reactive power does not result in real energy consumption, it plays a crucial role in ensuring
the electromagnetic fields necessary for the operation of AC systems, and contributes to the stability
and efficiency of electrical networks.
Apparent power represents the total power delivered by an energy source to an electrical system. It
combines both the active power (P), which performs useful work, and the reactive power (Q), which
supports the energy exchange necessary for electromagnetic processes. Apparent power is measured in
volt-amperes (VA).

Formula:

S=U⋅IS = U \cdot I

Where:

 SS — apparent power (VA)

 UU — voltage (V)
 II — current (A)

Key Concepts:

1. Active Power (P): The portion of power used to perform actual work, such as heating or
lighting. Measured in watts (W).
2. Reactive Power (Q): The portion of power that flows back and forth between source and
reactive components, used to sustain electric and magnetic fields. Measured in volt-amperes
reactive (VAR).
3. Power Factor (cos φ): The ratio of active power to apparent power. It reflects the efficiency of
power usage. A power factor close to 1 indicates efficient energy consumption.

cos⁡(φ)=PS\cos(\varphi) = \frac{P}{S}

Apparent power is essential in electrical system design and analysis, as it defines the full capacity
required from generators and transformers. It reflects the combined effect of real energy consumption
and reactive energy flow, helping engineers size equipment appropriately.
 The relationship between these types of power is illustrated by the so-called power triangle:

S ^2 = P ^2 + Q ^2

This graphical representation makes it possible to understand how much of the supplied
energy is actually consumed (P) and how much is only circulated (Q).

 Explain the principle of operation and area of application of electronics element –

diode

Diode: Principle of Operation and Applications

1. Operating Principle

A diode is a semiconductor component that permits electric current to flow in only one direction. This
unidirectional behavior is the key to its functionality in electronic circuits, allowing it to act as an
electronic one-way valve.

Diode Behavior in AC Circuits

When connected to an alternating current (AC) source, a diode blocks one of the half-cycles of the
waveform. As a result, only the positive (or negative) portions of the current are allowed to pass,
producing a pulsed output aligned with the allowed half-cycle.
Types of Rectifiers Using Diodes

There are two basic rectifier types based on diode configurations:

 Half-Wave Rectifier:
Allows only one half (typically the positive) of the AC cycle through, cutting off the other half.
This results in a pulsating DC output with lower average voltage.
 Full-Wave Rectifier (Bridge Configuration):
Utilizes four diodes in a bridge layout to rectify both halves of the AC input. Each half-cycle
activates two diodes, ensuring continuous current flow in one direction through the load. This
yields a more efficient full-wave rectified output.

. Diode Bridge Rectifier Operation

A bridge rectifier converts AC to DC using four diodes arranged in a specific configuration:

 Positive Half-Cycle: Diodes D1 and D2 conduct, directing current through the load in a
consistent direction.
 Negative Half-Cycle: Diodes D3 and D4 conduct, again pushing current through the load in
the same direction.

This method results in a full-wave rectified output — both halves of the AC signal are used to
produce a pulsating direct current.

Use of Filters in Rectification

Despite rectification, the resulting DC still contains ripples — small fluctuations in voltage. To
smooth the output and obtain a steady DC signal, filter circuits (often using capacitors or inductors)
are added after the rectifier.

Importance of Rctifiers in Electronics

Rectifiers are fundamental components in modern electronics. Since most electronic devices require
direct current (DC) for proper operation, rectifiers serve as essential elements for converting AC
from the power grid into usable DC, enabling everything from phone chargers to industrial
machines.