electronic components

A varistor is a name used for "variable resistor". The ones that I see are like potentiometers that have three leads. One for each end of a resistive track and one the is able to be moved to different locations along the track.

Test one: Find the two end points and measure the resistance while moving the variable contact. You should see NO change in the measured value.

Test two: Measure the resistance from one end to the adjustable contact. Move the adjustable contact from one full extreme to the other and measure the resistance along the way. You should see the resistance vary as you move the contact.

Points to note: The resistance scale on most of these are not "linear". That means that they don't vary by the same amount per degree of turn. Some change by the same percentage, others multply by factors of 10, others vary by the square of the value.

For more detail on this and the measurement of the other parts you have nominated, there are handy data sheets on the internet for all of them. Just "ask" your search engine to find the product. If you know a manufacturer of the chip you are interested in, then enter that to. You will find very specific help in that format.

The challenge for you is how much to spend on good instruments for your measurements.

WHAT?

Varistor is a voltage dependant resistor. What you are describing is a potentiometer. the varistor is actually a two electrode semiconductor, having non-linear resistance.

Wangito.

Yes you are all correct, got it wrong.

Please disregard post 1 and follow the advice of the others that have responded.

Sorry for the confusion.

A varistor is also known as a surge suppressor and also as a voltage dependent resistor (VDR). It's a semiconductor device whose resistance decreases rapidly when the threshold voltage is reached and/or exceeded.

It's used to protect circuits from voltage transients such as those coming from relays/contactors. To some extent, they may protect a circuit from lightning transients from the power lines (this usually results in the varistor's demise, however).

With regards to the other devices...I just got lazy .

oooo,

many questions one after another

go

http://en.wikipedia.org/wiki/Transistor

http://www.wisegeek.com/what-is-a-varistor.htm

http://en.wikipedia.org/wiki/Varistor