# Basic radio theory, circuits and calculations

### Tolerance and effect of temperature on components

These are important aspects of all electronic components, particularly resistors and capacitors.

Tolerance
The tolerance on the value of a component is a measure of how accurate its value is. For example, a resistor of nominal value l0,000, and a tolerance of±10%, may have an actual resistance between 9,000 (ie 10,000- l0%)and 11,000 (ie 10,000+ 10%). The usual tolerances on the values of resistors and capacitors are ±20, ±10, ±5, ±2 and ±1%.

Temperature effects

Generally the value of a component increases as the temperature increases. A constant known as the 'temperature coefficient' is a measure of this increase, and thus (for most items) the temperature coefficient is positive.

There are a few exceptions, eg ceramic capacitors having a negative temperature coefficient can be made. Carbon and semiconductors have a negative coefficient.

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