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Understanding our Ohm's law watches and clock design....what the formulas represent, how to read the resistor band color chart, and which product is right for you!

Preparing for a Electrician's Professional Exam?  Order your Ohm's Law Power Wheel Watch Today! All the electrical and electronics formulas you need!
Resistor Band Instructions Below

AC Ohms Law Chart PosterAC Alternating Current Ohm's law power formulas.
Generally, if you are a MASTER electrician,
troubleshooter, or electrical engineer,  you may prefer
this Ohms law watch or clock product.
Think Impedance -  Need Z formulas?

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DC Ohm's Law Chart
DC Direct Current Ohm's law power formulas.  Generally, if you are an electrician, electronics technician, journeyman, apprentice, student or  hobbyist you may prefer this Ohms law watch or clock product.  Think resistance - Need R formulas?  As you advance in your training you will, no doubt, find the AC formulas handy also. "It's 10:09 and 43ohms....never fumble for  those hard-to-remember Ohms law formulas again...." 
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TechNote for Quadrants:  The face is arranged in four quarters.  To find the missing value of any of the center components, select one of three corresponding formulas in that quadrant.  We call these two designs our AC and DC models.  See below for info on the resistor color chart in each hour's position. 

You should know by looking at the face which design (AC or DC Ohms Law formulas)  is right for you.  If you need further information, please keep reading.  Most students of electricity begin their study with what is known as direct current (DC), which is electricity flowing in a constant direction, and/or possessing a voltage with constant polarity. DC is the kind of electricity made by a battery (with definite positive and negative terminals), or the kind of charge generated by rubbing certain types of materials against each other.

AC Alternating Current Theory: Ohm's law defines the relationships  between (AP) apparent power, (ET) voltage total, (IT) current total, and (Z) impedance. 

Alternating Current - as in the electrical outlets in our homes, the flow (current) of electricity is always changing direction (60 times every second in the U.S., 50 times every second in other countries), through the loads such as lamps, water heaters, televisions, and all the things we plug into the wall outlets.  These items also have resistance, but because of the alternating current, we have to change our mathematics starting with R or RESISTANCE being replaced by a thing called IMPEDANCE or the letter Z.  Now, if we think about water flowing in the river again, but this time with the flow (current) changing direction 50 or 60 times in every second, we can imagine some very big differences in the DC and AC theories.  The AC theory is mostly used in journeyman ship levels through upper engineering people.

DC Direct Current Theory: Ohm's Law theory defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance.

Direct Current - Most students of electricity begin their study with what is known as direct current (DC), which is electricity flowing in a constant direction, and/or possessing a voltage with constant polarity.  As in an automotive battery, the flow (current) of electricity is always moving in one single direction from one battery connection through the load (a light bulb, a motor, the radio or any other device in a car), back home again to the second connection of the battery.  In DC, the loads all have different measurements of resistance to the flow or current.  The resistance is represented by the letter R in electrical formulas.  I like to think of water flowing in a river with a regulated dam causing resistance to the flow.  The DC theory is used mostly in early training years and almost always in electronics.

TECHNOTE:  Impedance is to AC as resistance is to DC. While both quantities are expressed in “ohms,” the former requires higher math (trigonometry and calculus); the latter can pretty much be ciphered in your head, but you will still find our Ohm's law watches helpful, either way. 

TechNote for resistor band color card or chart:  A copy of  how to read the our "Magic Wheel" or "Power Wheel"  resistor band color chart  will be included with your ohm's law watch or clock when it is shipped to you, along with warranty info. 

The color at each hour on your Ohm's law watch  is purposely positioned at the number of that color’s value.  This will help you to identify the value for each resistor.  For example, the 12:00 black band position represents the value of “0"; the 1:00 brown represents the value of “1";  and so on consecutively up to  the  9:00 “white” representing the value of “9".  The 10:00 silver  (or 10 min. to)  represents 10% tolerance, and the 11:00 gold band position (or 5 min. to) represents 5% tolerance.  With this in mind you should be able to read the resistor bands for easy identifying.  For more on resistors, and how to read resistor band colors, please go to our resistor page:

Our Ohm's law watch and clock products are great for ham radio operators,  students studying electronics or electrical theory, electrician's, troubleshooters, engineers,  apprentices, master electrician's, electrical contractors, college classrooms, and anyone in the electrical  and electronics fields!  We hope you find our products helpful in the office and in the field. 

  • DC TechNote:   Resistance in a circuit can be called the LOAD... and can be represented by the symbol for resistance R
  • DC TechNote:  In DC circuits the direct of current flow is CONSTANT.  In AC circuits the direction  of current flow REVERSES periodically.
  • DC TechNote:  DC circuits are the foundation for your understanding of AC circuitry.
  • AC TechNote:  Impedance( Z): In a purely resistive circuit such as a DC (direct current ) circuit, you can use Ohms law and the    Resistance formulas, but in an AC (alternating current) circuit the opposition to the flow of current is called impedance. The symbol for Impedance is Z . To use impedance in the Ohms law  formulas replace the R for   resistance with the Z for impedance.
  • AC TechNote  From  im·ped·ance   (m-p d ns)
    Symbol Z A measure of the total opposition to current flow in an alternating current circuit, made up of two components, ohmic resistance and reactance, and usually represented in complex notation as Z = R + iX, where R is the ohmic resistance and X is the reactance.  See our impedance page for more info.
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