Ohm's Law

by Frederick Hoehn, copyright 2012.

George Simon Ohm gave us the formula, I x R = E.  You multiply your electrical current in amperes (amps), times your electrical resistance in Ohm’s, and you get your voltage in volts.  I suspect that it was God who showed George.  

This is Ohm’s Law for d.c. circuits (direct current).  Things get a little more complicated for a.c. circuits (alternating current, like you have at home in the U.S.)

In a.c. circuits, you have your resistance, and also you have your inductive reactance, and your capacitive reactance.  The impedance (Z) is the vector sum of those three things, and often results in changing the phase angle of the current relative to the voltage.

A mnemonic device for this is “ELI the ICE man”, which reminds us that in mainly inductive circuits (L for inductance), the voltage (E) leads the current (I), while in mainly capacitive circuits (C for capacitance) the current leads the voltage.

As an example of Ohm’s Law, if you have a hundred ohm resistor, and apply a voltage of one hundred volts, how much current will flow?  The only answer Ohm’s Law will give us is one amp, because one times one hundred yields one hundred.  

That was Ohm’s Law for current, resistance, and voltage.

But there’s another law.  It’s P = I x E.  The power (P) in watts equals the current (I) in amps multiplied by the voltage (E) in volts.  

For that same hundred ohm resistor with one amp of current flowing, the power would be one hundred watts, so that resistor needs to be fairly large physically, because a little half watt resistor would burn out under those circumstances.

If you live in an older building, you don’t want to draw too many amps of current, and trip the breaker or blow the fuse.  If you want to buy that newfangled cooking appliance you saw on TV, can you use it without tripping the breaker?

Take the wattage of the appliance, perhaps it might be 1500 watts and divide by the voltage of 115 volts, and you get about 13 amps.  Now add that to the number of amps being used by your other appliances that you’ll be using at the same time, (color TV? small room heater?) and see if it exceeds your 25 amp or 35 amp circuit breaker, as the case may be. 

Speaking of cooking, let me give you a quick recipe.  This recipe came from my Grandmother, who was from Sweden.  My Mother was watching my Grandmother cook.  Grandmother added an ingredient to the food.  My Mother asked Gramma, “How much of that, Mother?”  Grandmother answered, “Yust ‘til you tink it’s enough.”

And you can use that recipe with a lot of meals.  But ask God to help you with what you think is enough.  When you pray, believe you receive what you’re asking for, and you shall have it, from Mark 11:24, says Jesus.