Electronic Components and Electrical Materials Explained

Electronic Components & Electrical Materials

Resistors: Types and Characteristics

Understanding Electrical Resistance

Resistance is the property of a material that hinders the passage of electric current through it.

Ohmic Resistance Explained

Ohmic resistance refers to the resistance of materials where the current is directly proportional to the voltage across them, following Ohm's Law.

Fixed Resistors: Construction & Use

A fixed resistor typically comprises a cylindrical insulating support on which a layer of resistive material, often pulverized charcoal mixed with binder substances, is deposited.

Variable Resistors: Potentiometers & More

A variable resistor, such as a potentiometer, has an ohmic value that varies within certain limits according to the displacement of a movable contact. This variation can be achieved through angular displacement (rotary) or via linear actuators. For instance, turning a potentiometer knob varies the resistance.

Specialized Resistors for Specific Needs

• NTC (Negative Temperature Coefficient) Resistors: Their internal resistance decreases with increasing temperature.
• PTC (Positive Temperature Coefficient) Resistors: Their internal resistance increases with increasing temperature.
• LDR (Light-Dependent Resistor): Their resistance varies with the intensity of light striking them. This photoconductivity means that as light intensity increases, their resistance decreases, allowing a greater current flow (e.g., an ammeter would read a higher current).
• VDR (Voltage-Dependent Resistor): Their ohmic value decreases with increasing electric voltage across them.

Capacitors: Storing Electrical Energy

A capacitor is a device capable of storing electric charge to transfer it when needed. It typically consists of two parallel metal plates (often aluminum) separated by a dielectric (insulating material). Two conductors, which serve as the connection terminals, are welded to these metal plates.

Classifying Electrical Materials

Insulating Materials: Blocking Current

Insulating materials are those that do not allow the passage of electric current. They typically have 8 valence electrons in their outermost shell.

Conductive Materials: Allowing Current Flow

Conductive materials are those that allow electric current to pass easily. They typically have 1 or 7 valence electrons in their outermost shell.

Semiconductor Materials: Controlled Conductivity

Semiconductor materials lie between conductors and insulators. They conduct electricity only under certain conditions and typically have 4 valence electrons.

Semiconductors are materials that are insulators under normal conditions but become conductors when subjected to a source of electric power, thermal energy, light, or by a process called doping. This is why a silicon crystal is nearly a perfect insulator at room temperature; as the temperature rises, its conductivity increases.

Intrinsic Semiconductors: Pure Elements

Intrinsic (pure) semiconductors like Silicon (Si, ~0.7V bandgap) and Germanium (Ge, ~0.3V bandgap) exhibit decreasing resistance with increasing temperature, a behavior opposite to that of metals.

Extrinsic Semiconductors: Doping Effects

Depending on the doping material, semiconductors can be classified as extrinsic:

• N-type Extrinsic Semiconductors: Formed by adding pentavalent impurities (elements with 5 valence electrons in their outermost orbit), which introduce excess free electrons.
• P-type Extrinsic Semiconductors: Formed by adding trivalent impurities (elements with 3 valence electrons in their outermost orbital), such as boron, which create 'holes' (electron deficiencies) in the silicon or germanium lattice.