Resistors:
A resistor is a two-terminal electrical or electronic component that resists an electric current by producing a voltage drop between its terminals in accordance with Ohm's law: The electrical resistance is equal to the voltage drop across the resistor divided by the current through the resistor.
The resistance of a resistor is given by the formula
R = ρ . 1 / A
where:
· ρ is the resistivity of the material that the resistor is made from
· l is the length of the resistive material, between the end contacts
· A is the (presumed uniform) cross sectional area of the resistive material
or R = V / I
Capacitors:
A capacitor is a passive electronic component that stores energy in the form of an electrostatic field. In its simplest form, a capacitor consists of two conducting plates separated by an insulating material called the dielectric. Capacitance is directly proportional to the surface areas of the plates, and is inversely proportional to the plates' separation. Capacitance also depends on the dielectric constant of the dielectric material separating the plates. The capacitor's capacitance (C) is a measure of the amount of charge (Q) stored on each plate for a given potential difference or voltage (V) which appears between the plates:
C = Q /V
The standard units of Capacitance,
farad: F
microfarad: μF (1 μF = 10-6 F)
nanofarad: nF (1 nF = 10-9 F)
picofarad: pF (1 pF = 10-12 F)
Diodes:
A diode is an electrical device allowing current to move through it in one direction with far greater ease than in the other. The most common kind of diode in modern circuit design is the semiconductor diode, although other diode technologies exist.
Forward Bias : When the p region of the diode connected to the positive terminal of battery, the diode is said to be in forward bias.
Reverse Bias : When the p region of the diode is connected to the negative terminal of the battery.
Light Emitted Diode (LED):
An LED is a special semiconductor which emits light when current is passed through it. It is transducer which converts electrical energy to light. It is generally used to indicate if there is a voltage. The red, green, yellow and amber have a working voltage of approximately 1.8 volts. The actual working voltage is determined by the breakdown voltage of the particular semiconductor material.
