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??? These questions are fairly straight forward, so I'm only going to show the working out on question one, and give the answers to the rest. If you got them wrong, and can't figure out where, let me know and I'll see if I can help you. Any way the solution for question one is as follows:

??? The remaining answers are as follows: Q.2 = 0.2A, Q.3 = 3.6mA, Q.4 = 50mA

??? It has occurred to me that If we have some true beginners on the list a brief explanation of the resistor color code might be useful. I'll start off with a quick picture of the color code, explanation to follow.

??? On most Resistors you see in electronics kits you will see four bands of colors. These colors allow us to know the value of the resistor. The above picture may or may not be totally confusing to you, but isn't really that hard to understand. The important part of the color band system, at least for most people actually building something, is the first three bands. I'll deal with the forth band and what it means later.

?????? The first two bands, are the ACTUAL "value" of the resistor. say we have a resistor with the following colors:????

??? So, we have?? Red - Red. If you look at the chart above, we will see that Red corresponds to the value "2", so Red - Red equals 2 - 2. The third band is Green. This is what is called the "Multiplier". In this case Green equals 5, so we need to add 5 zeros, or Multiply by 10^5. We have now gathered enough information about the resistor to tell us the value. Using the first two colors we know that the "Value" is 22, Using the third color we know the multiplier is 5. Lets put this together. 2200000. That is 22 with 5 zeros added to the end. That makes the calculated value 2,200,000 Ohms. or more commonly, 2M2 Ohms. (That is 2.2 Mega Ohms).

???? Here are some more examples, and the solutions:????

On the first resistor we have Red - Black - Black????? That means it is 2 - 0 and no multiplier.....???? or 20 Ohms
On the second resistor????????? Brown - Black - Red???? That means it is 1 - 0 and 10^2 multiplier????? or 1000 Ohms
On the third resistor???????????? Yellow Violet Green???????????????????????? or? 4 - 7? and 10^5?????????????????? or 4700000 Ohms
on the forth resistor????????????? Green - Red - Brown?????????????????????? or 5 - 2? and 10^1??????????????????? or 520 Ohms

??? One further thing, the forth band. This is the "Tolerance" band. Remembering that these devices are manufactured in bulk. Like any mass produced object there are unavoidable? inaccuracies in their manufacture. If you take you normal run of the mill Resistor and measure it with an Ohm meter, you will of course find there is some difference between the value written on the resistor and the ACTUAL measured value. Manufacturers use the forth band on the resistor to indicate how far outside this value the ACTUAL value might be. On a four band resistor, typically this band will be either gold or silver. To give an example say we have a resistor with Brown - Black - Red - Silver. The value is 1 - 0 - and 10^2 multiplier. Or 1000 Ohms. How does the silver band affect this?? A silver band means the component has a 10% tolerance. 10% of 1000 is 100, so the possible manufactured error is 1000 Ohms + or - 100 ohms. This means that the actual measured resistance will be some where between 900 Ohms and 1100 Ohms. On the average every day flashing light or siren kit from tandy, this is "close enough". Sometime however it is necessary to have the resistance a bit closer to the desired tolerance, so you might use a resistor with 5% tolerance (gold band), or even 1% these resistors have five bands but are read basically the same way.

??? Another thing to worry about is interpreting the various ways you will find the value for a set resistance written down. it is obviously inconvenient to continually write 1,000,000 Ohms all the time. or even 1,500. So we use the common Kilo and Mega prefixes to designate thousands and millions. So 1k Ohm equals 1000 Ohms and 1 Mega Ohm equals 1,000,000 Ohms. Things get a bit more complicated here how ever. In the old times, (when I was a lad) it was common to talk about Ohms or decimal parts there of with a decimal point. So 1.5k was 1500 Ohms. 2.2k was 2200 Ohms. I imagine there is a good reason, but nowadays they have changed this, and now the convention is: 1k5 equals 1500 Ohms, and 2k2 would be 2200 Ohms. Like wise with Mega Ohms. 4M7 would be 4,700,000 and 5M6 would be 5,600,000. I imagine The reason could be for clarity. I imagine that it might be really easy to miss a small decimal point and use the wrong resistor. Even looking at what i've just typed here on my 17" monitor it is awful hard to see the decimal points and so easy to confuse 1.5 with 15. However it is a little more harder to miss a "k" or an "M".

??? Something else that you may see. It is now becoming very common to see Surface mount devices in even hobbyist electronics. Surface mount resistors come in several forms. There are small legless barrel looking types, imagine a small resister without legs,? these packages are called Melf, or the smaller version, MimiMelf. These are from what i've seen usually labeled with color bands, and can be read in much the same way as normal resistors. Another version you might run across is the 1206, or 0805 "Chip" resistor. These are small rectangular flat looking things, with silver ends. Usually, they have the value written on the top surface, in the case of the 1206 package (at least as I know it to be called) it is fairly easy to read the writing. However the 0805 package is allot smaller and you might wish to use some optical assistance to read it. When you look at these resistors, you will see four numbers on the top. The first three represent the "Value" and the forth the multiplier. So 4703 would be 470 multiplied by 10^3 or 470,000 that is 470k.Like wise 1002 would be 10,000 Ohms or 10k Ohms. Things get a little different when you go bellow 1k Ohm. This would be 1001, or 1,000 Ohms. When you get below 1000 Ohms,? they change the designation slightly. 100 Ohms is designated 100R likewise 47 Ohms would be written 47R0. This is fairly easy to understand if you can actually read the bloody thing. An 0805 package for instance is around 2mm long and 1mm wide. This makes the writing VERY small.

??? I'd love to show you some pictures, but fate is conspiring against me EVER buying a scanner to suit my aging computer it seems. Hopefully soon.......

??? O.K. so I'm not a teacher, but I hope that you have been able to understand at least SOMETHING of what I have written here without being totally confused out of your brains. Next time, as promised i'll have a quick look at series/parallel resistors and how to have all sorts of fun solving these problems..........

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