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A passive electronic compoenent will typically absorb energy without create any active gain. These are some of the common passive electronic components. One other passive component is the diode however I've included that in the semiconductors.
A resistor is the most simiple electronic component. I resists the flow of current through a circuit. The end result is a voltage drop (loss in potential) and power being absorbed within the device. Every electrical device, cable or connection has resistance in it, but for most circuits the resistance within the wiring can be ignored.
The resistance is measured in ohms (Ω) and varies from only a few ohms (or even less if you are considering the normal cabling) to many mega ohms (MΩ).
A resistor is normally a small cylindrical device which has different coloured bands indicating the resistance value. For more details see the resistor
colour code scheme.
A light dependent resistor (LDR), sometimes called a photoresistor is a special kind of resistor whose resistance varies depeding upon the amount of light on it's exposed surface.
Different LDRs can have different properties, but a typical one may have a resistance measured in kΩ when in bright light to MΩ when dark.
A capacitor can be used in a variety of different ways. Some common uses in electronic circuits are listed below:
The effective "size" of the capacitor is measured in farads (F). The capacity of capacitors used in electronic circuits is very small and is normally referenced as micro-farads (μF), nano-farads (nF) or pico-farads (pF).
Capacitors are made of different diaelectrics according to the size of the capacitor and to its intended use. In order of size (smallest capacity to highest) these are usually ceramic, polyester and electrolytic. The ceramic and polyester capacitors can be connected either way around, but the electrolytic capacitors have a positive and negative terminal that must be connected accordingly.
Note that the plus sign on the second example indicates the polarity for an electrolytic capacitor.
Please view the copyright information regarding use of the circuits.