Understanding Electrical Circuits and Components
Electric Current and Circuits
Direct Current (DC)
Direct current (DC) involves a constant voltage between two points, with electrons flowing in a single direction, from the positive (+) pole to the negative (-) pole. DC power sources include batteries and dynamos.
Alternating Current (AC)
Alternating current (AC) involves a cyclical voltage that repeatedly changes over time, starting at zero, reaching a maximum, decreasing back to zero, then going negative before returning to zero. AC power is generated by alternators.
Current Intensity
Current intensity measures the amount of electric charge flowing through a conductor per unit of time. It’s measured in amperes (A) using an ammeter.
Circuit Components
- Limiting Device: Opens or closes a circuit.
- Resistor: Reduces current flow within a circuit.
- LED (Light Emitting Diode): Allows current to flow in only one direction, converting electrical energy into light of a single wavelength. An optimal current for an LED is 20 mA, often requiring a resistor in series to prevent damage.
- Motor: Transforms electrical energy into mechanical energy.
- Button (Switch): A temporary switch. Normally Open: Allows current flow when pressed. Normally Closed: Blocks current flow when pressed.
- Fuse: A protective element placed in series within a circuit to prevent damage from excessive current.
- Dynamo: Generates continuous direct current (DC) by converting mechanical energy into electrical energy.
- Alternator: Generates alternating current (AC) by converting mechanical energy into electrical energy.
- Battery: Produces electrical energy through a chemical reaction.
- Electrical Receiver: Converts electrical energy into another form of energy. Examples include motors, lamps, LEDs, buzzers, speakers, resistors, and electromagnets.
Diodes and Semiconductors
Diode Functionality
A diode controls the flow of electric current, allowing passage in only one direction. It consists of two semiconductor crystals: an N-type cathode (provides electrons) and a P-type anode (accepts electrons).
Reverse Bias
In reverse bias, a diode acts as an insulator, blocking current flow. The negative (-) pole of the power supply connects to the anode, and the positive (+) pole connects to the cathode. A resistor is typically inserted in series with the diode.
Forward Bias
In forward bias, a diode acts as a conductor. The positive (+) pole of the power supply connects to the anode, and the negative (-) pole connects to the cathode. A resistor is typically inserted in series with the diode.
Semiconductors
Semiconductors act as conductors at high temperatures and insulators at low temperatures.
- Intrinsic: Composed of silicon or germanium.
- Extrinsic: Composed of silicon or germanium doped with arsenic or boron.
Sensors
- NTC and PTC: Temperature sensors.
- Potentiometer: Position sensor.
- VDR: Voltage sensor.
- LDR: Light sensor.
- Gauges: Pressure sensors.
Capacitors, Coils, and Integrated Circuits
Capacitor
A capacitor stores electric charge. It consists of two metal sheets separated by an insulator called a dielectric. Capacitance is measured in farads (F), but smaller units like picofarads (pF), nanofarads (nF), and microfarads (µF) are commonly used.
Coil (Inductor)
A coil consists of insulated wire wound around a cylinder made of air, metal, or ferrite. It opposes changes in current due to the magnetic field it creates. Inductance is measured in henries (H), but smaller units like microhenries (µH) and millihenries (mH) are commonly used.
Integrated Circuit (IC)
An integrated circuit (IC) is a miniaturized electronic circuit on a microchip, often housed in a plastic package. ICs contain millions of interconnected components and are identified by letters and numbers printed on their surface.
Chip
A chip is a miniaturized electronic circuit that can replace numerous discrete components.
Printed Circuit Board (PCB)
A printed circuit board (PCB) provides the base and connections for electronic components.
Planar Technology
Planar technology involves creating microchips on thin silicon wafers using photolithographic processes. Masks are used to print the circuit design onto the chip, layer by layer. Robert Noyce pioneered this technique.
The first chip was built by Jack Kilby in 1958.