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Starting electronics
Take note — Take note — Take note — Take note
This is a vitally important concept — probably the
most important one in the whole world of electronics
— and yet it is often misunderstood. Even if it is not
misunderstood, it is often misinterpreted.
Indeed, this is so important, let’s recap it and see what it all
means:
If a voltage (V — measured in volts) is applied across a resistance
(R — measured in ohms), a current (I — measured
in amps) will flow. The voltage, current and resistance are
related by the expression (1):
The importance of this is that the current which flows depends
entirely on the values of the resistance and the voltage. The
value of the current may be determined simply by rearranging
expression 1, so that it gives (2):
(1)
So, a voltage of say 10 V, applied across a resistance of 20 Ω,
produces a current of:
(2)
Similarly, if we have a resistance, and a current is made to
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