.
1
is quite small for electronics so resistances are often given in
k
and M.
1 k
= 1000
1 M
= 1000000 .
Next Page: Ohm's Law
Also See: Voltage and Current |
Resistors | Series and Parallel |
Impedance
Resistance is measured in ohms, the symbol for ohm is an omega
.
1
is quite small for electronics so resistances are often given in
k
and M.
1 k
= 1000
1 M
= 1000000 .
Resistors used in electronics can have resistances as low as 0.1
or as high as 10
M.
When resistors are connected in series their combined resistance is equal to the
individual resistances added together. For example if resistors R1 and R2 are
connected in series their combined resistance, R, is given by:
Combined resistance in series: R = R1 + R2
This can be extended for more resistors: R = R1 + R2 + R3 + R4 + ...
Note that the combined resistance in series will always be greater than any of
the individual resistances.
When resistors are connected in parallel their combined resistance is less than any
of the individual resistances. There is a special equation for the combined resistance
of two resistors R1 and R2:
| Combined resistance of two resistors in parallel: |
R = | R1 × R2 |
| R1 + R2 |
For more than two resistors connected in parallel a more difficult equation must be used. This adds up the reciprocal ("one over") of each resistance to give the reciprocal of the combined resistance, R:
| 1 | = | 1 | + | 1 | + | 1 | + ... |
| R | R1 | R2 | R3 |
The simpler equation for two resistors in parallel is much easier to use!
Note that the combined resistance in parallel will always be less than any of the individual resistances.
Materials can be divided into three groups:
