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Ohm’s Law
Ohm’s law defines the relationships between current, voltage and resistance.
A good way to understand ohm’s law is an analogy with a domestic water system. The same way that an electric current flows through a copper wire, water flows through a copper pipe in a water system. Most people do not think to much about the fact but when they turn on tap the water comes out as a result of the pressure that is provided by a pumping station some miles away. This water pressure is similar to that used to drive electricity around a circuit, the potential difference or pd for short is the term that is used.
1 Ohm
Can be defined as the amount of resistance that will produce a potential difference (p.d.) or voltage of 1 Volt across it when a current of 1 Ampere flowing through it.
1 Ampere
Can be defined as the amount of current which, when flowing through a resistance of 1 Ohm will produce a potential difference of 1 Volt across the resistance.
1 Volt
Can be defined as the difference in potential (voltage) produced across a resistance of 1 Ohm through which a current of 1 Ampere is flowing.
“When the temperature is constant, the potential difference across the ends of a resistance is proportional to the current flowing through it”
One of the easiest formulas to understand and one that can point to many problems in old radio and TV sets.
Frank
A useful way for beginners to remember Ohms Law;
If you use E instead of V (E = Electromotive Force) and put the three letters in a triangle, ignore the one you want to find and the other two letters give you the formula.
If combined with the formula for power – W = EI – you can get additional useful formulae to use when you know the resistance but only one of the other values, thus:
E²
W = — and W = i²R
R
The commonest mistake that is made with Ohm’s law is the “When the temperature is constant” bit. Ignore it at your peril!
Oops!
‘put the three letters in a triangle’ shoulf have read: put the three letters in a triangle in alphabetical order.
That’s the reason for using E for voltage!
I used the triangle but I was OK with V for voltage, the V/IR just worked for me but yes I can see the merits of E/IR with it being in alphabetical order.
Frank