# Basic Electronics

It is important to understand some simple, general principles in order to have a full grasp of Electricity and Electronics

## What is CR Circuit?

A CR circuit is one that contains both capacitors and resistors (either in series or in parallel). The action of a CR circuit upon a sine wave is to change both the amplitude and the phase of the output signal as compared to the input signal. Universal amplitude/phase tables can be prepared, using the time […]

## What is Reactance of Capacitor?

The reactance of a capacitor for a sine wave signal is given by: where C is the capacitance, in farads and f is frequency, in hertz. Reactance is measured in units of ohms and is defined by the ratio: ˜V/˜I or v/i using the convention noted below, where ˜V is the AC voltage across the […]

## Time Constants Of Capacitor

The charging and discharging of a capacitor is never instant. When a sudden step of voltage is applied to one plate of a capacitor, the other plate voltage will step in voltage by the same amount. If a resistor is present that connects the second plate to a different voltage level the capacitor will then […]

## Energy and Charge Storage by Capacitor

The amount of charge stored by a capacitor is given by Q = CV, and when C is given in μF and V in volts, charge Q is then in microcoulombs (μC). How much charge is stored by a 0.1 μF capacitor charged to 50 V? Using Q = CV with C in μF, V […]

## Construction of Capacitors

Like resistors, capacitors can be obtained in the older wire-connected style or more commonly now, as SMD components. Small-value capacitors can be made using thin plates of insulating material (a dielectric) metallized on each side to form the conductors. Thin plates can be stacked and interconnected (Figure-c), to form larger capacitance values up to 1000 […]

## The Parallel Plate Capacitor & Relative Permittivity

The parallel-plate capacitor is the simplest theoretical and practical arrangement and its capacitance value is, for ideal conditions, easy to calculate. For a pair of parallel plates of equal area A, separation d, the capacitance is given by: The quantity εε0 is a universal constant called the permittivity of free space, and it has the […]

## What is Capacitance?

Two conductors that are not connected and are separated by an insulator constitute a capacitor. When a source of EMF such as a cell is connected to such an arrangement, current flows momentarily, transferring change (in the form of electrons) from one conducting plate (the + plate) to the other. When a quantity of charge […]

## What is Thermistors?

Thermistors are resistors made from materials that have large values of temperature coefficient. Both PTC and NTC types are produced for applications that range from temperature measurement to transient current suppression. Figure shows some representative types. Miniature thermistors either in bead form or in glass tubes are used for temperature measurement, using a bridge circuit […]

## Resistors In Circuit Obey Ohm’s Law, Kirchoff’s Law and Superposition/ Thevenin Theorem

Resistors in a circuit obey Ohm’s circuit law and Kirchoff ’s laws. Ohm’s circuit law is written in its three forms as: V = RI, or R = V/I or I = V/R Where V is voltage across two points, ‘I’ is the current flowing between the points and ‘R’ is the (constant) resistance between […]

## Law of Variable Resistor | Potentiometer Laws

The law of a variable resistor or potentiometer must be specified in addition to the quantities that are specified for any fixed resistor. Potentiometer Laws The potentiometer law (called taper in the USA) describes the way in which resistance between the slider and one contact varies as the slider is rotated; the law is illustrated […]

## Power Dissipation and Temperature Rise

The power dissipation rating (P), measured in watts (W), for a resistor indicates how much power can be converted to heat without damage to the resistor caused by its rise in temperature. The rating is closely linked to the physical size of the resistor, so that ¼Wresistors are much smaller than 1 W resistors of […]

## Resistor Characteristics Include Ranges, Temperature, Stability and Noise Level

Important characteristics of resistor types include resistance ranges, usable temperature range, stability, noise level, and temperature coefficient. Wire wound resistors are available in values that range from fractions of an ohm (usually 0R22) up to about 10 kW (though higher values up to 100 Kw are available). Carbon composition resistors can be obtained in ranges […]

## Surface Mounted Resistors

Two forms of coding are used for surface mounted resistors and capacitors. The three-symbol code uses two digits for the significant figures and one as multiplier, so that 471 = 47×10 = 470W and 563 = 5K6. Values below 10 are indicated in BS1852 form, so that 2R2 = 2.2W. The alternative marking, which is […]

## What is Tolerances and E-series

Any mass-production process that is aimed at producing a target value of a measurable quantity will inevitably produce a range of values that are centered around the desired value and for which a maximum tolerance can be specified. The tolerance is the maximum difference between any actual value and the target value, usually expressed as […]

## Resistance Value Coding | Resistor Color Coding

Values of resistors (and capacitors) that use conventional wire mounting are usually indicated by a set of coloured bands (Figure). At one time, three bands were used, allowing two significant digits and one multiplier figure, but because of the widespread use of close-tolerance components, it is now more common to use four or five bands […]