Brainteasers – Issue 11, 2008
We all have used an acronym, mnemonic, rhyme, word association, or other technique to help us remember information, lists, events, etc. I know they work because most of them are still stuck in my head. See how many of the following you may remember.
Resistor Color Code
Color bands are used to represent numeric values in ohms on certain types of resistors. The numbers 0 through 9 are represented by the colors black, brown, red, orange, yellow, green, blue, violet, gray, and white respectively. The first and second band are typically the resistor’s first two significant digits, the third band is the number of zeros following the first two digits, and the forth band is the resistor’s tolerance. There are many variations to this type of resistor coding, but to recall the basic color order, you can memorize the saying ‘Better Be Right Or Your Great Big Venture Goes West’. A little investigation will most likely discover many other sayings for memorizing the resistor color code, some not as elegant as the one we have shared.
Visible Color Spectrum
To remember the main colors that we may see in a rainbow, or viewing the result of light that has traveled through a prism, think of Roy G. Biv. The colors with the longest to shortest wave length are Red, Orange, Yellow, Green, Blue, Indigo and Violet. You may have noticed that other than Indigo, the color spectrum order matches part of the Resistor Color Code.
ELI the ICE man
In an AC circuit involving inductance or capacitance, the voltage and current in the circuit will be out of phase with each other. An inductive circuit will cause a phase shift in one direction and a capacitive circuit will cause the opposite. To remember which is which, think of ELI the ICE man, where E = Voltage, I = Current, L = Inductor, and C = Capacitor, therefore: ELI (Inductive Circuit) – Voltage leads Current ICE (Capacitive Circuit) – Current leads Voltage
Solving algebraic expressions can be somewhat confusing unless we understand the order of operations that have been defined. Take the following equation: 7 + 6 / 2 – 2 * 3 = In which order do we solve the various elements? Can we take 7, add it to 6, then divide the result by 2, or maybe divide 6 by 2 and take the result away from 7? Luckily the order has been defined for us. We solve algebraic expressions by doing the computations in Parentheses first, if they are present, followed by Exponents, then either Multiplication or Division (order does not matter), and finally either Addition or Subtraction (again order does not matter). An easy way to remember this order is to memorize the saying ‘Please Excuse My Dear Aunt Sally’.
If you forget PI = 3.14159, you can get a quick approximation on a simple calculator by solving 22/7, or for more accuracy while just a bit harder to remember, solve 355/113.