Step 10: Cords and other things
I have added alligator clip attachments to the probe ends on my meter. They are a very handy accessory I got at Radio Shack. They are like an extra hand.
This toaster works well, and the meter shows a resistance reading due to the heating element inside the toaster. This is normal and good. This test could indicate there is a break in the circuit within the toaster. Further testing would be necessary to determine which part of the circuit is defective. Then a decision would need to be made as to whether the appliance can be repaired and whether it is worth the effort.
Whether it is a toaster, or a phone charger, or a power cord for a computer; cords often fray internally within an inch or two of the plug. This is very understandable. That is the area of the cord that is frequently flexed back and forth. If something, like a phone charger, works some of the time, but not at other times; attach the meter with a resistance scale setting. Gently flex the cord back and forth near the plug end. Make fairly sharp bends. Watch the meter reading to see if it fluctuates between a normal reading and no connection. If it does, ask someone with a soldering iron to cut the cord back and reattach the plug end for you.
This toaster works well, and the meter shows a resistance reading due to the heating element inside the toaster. This is normal and good. This test could indicate there is a break in the circuit within the toaster. Further testing would be necessary to determine which part of the circuit is defective. Then a decision would need to be made as to whether the appliance can be repaired and whether it is worth the effort.
Whether it is a toaster, or a phone charger, or a power cord for a computer; cords often fray internally within an inch or two of the plug. This is very understandable. That is the area of the cord that is frequently flexed back and forth. If something, like a phone charger, works some of the time, but not at other times; attach the meter with a resistance scale setting. Gently flex the cord back and forth near the plug end. Make fairly sharp bends. Watch the meter reading to see if it fluctuates between a normal reading and no connection. If it does, ask someone with a soldering iron to cut the cord back and reattach the plug end for you.
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Looking at the back/Bottom of the toaster. Im going to use OHMS Law to tell you what the reading on the meter should be close too.
My toaster is 220-240Volt 700Watt
remember R(OHMS) = V (Volts) / I (Amps) .... .... And P(Watt) = V * I .... .... And I = V / R
(Dont be put off by whats in the brackets or the capital letters), Have a go at it.
..so Whats my current flowing though the toaster ?
Is... .. I = P / V
IE. .. . 3.18Amps = 700W / 220 Volts
...............................................................................................................
... so the toaster uses 3.2Amps at 220Volts
OHMS law tells me that R =V / I
. . . . . . . . . 220 / 3.18 = 69.18Ohms
= = = = 69.18 Ohms at 220Volts
That is what ( I just farted ) the resistance should read on a typical 2 slice toaster at 220Volts
A toaster at 700W at 110V will be
.. .. 700 / 110 = 6.36Amps
.. .. . 110 / 6.36 = 17.3 OHMS
= = = = 17.3Ohms at 110Volts
Its not hard, Use Ohms law to check before or after. The result will be a little different but will be in the range. And besides if it is actually broken it will read ZERO ohms.
-Cactus
A correction however on the statement you made "And besides if it is actually broken it will read ZERO ohms".... while its a common error due to no reading on the meter, it isnt zero ohms, it's infinite ohms or an open circuit. I'd say 99% followed what you meant and didnt even catch that. I didnt until just now, passing over it, knowing what you meant... It's like proof reading your own work, it just doesnt help since you know what you mean. But keep up the good work!
I think i was drunk when i wrote that.
But its all good.
Resistance is directly relevant to Current and Voltage.
R = V / I
One person already commented 'skrubol' about the Resistant changes as metals rises in temperature, is true.
But im not sure how to measure the impedance of a wire glowing red hot . So im not sure how much of a difference it makes.
Maybe heat a wire with a lighter and measure its Resistance??
If it's reading zero ohms it will be tripping the breaker. If the conductor is broken it will read infinite ohms. Most meters represent this as 0L or sometimes as a 1 or 0 with no extra digits. Basically it will look the same as when the leads aren't connected to anything.
Several times I thought I wanted to learn electronics theory really, really well. Yet, I found my needs were always merely for some DC power adapter between 3 and 12 volts. As long as I knew how to do those projects, I was pretty well set.
I hope your sons enjoy the links you send.
If you look closely at my 120 volt toaster in step 10, the resistance reading for my toaster was 18.9 Ohms. Your calculations based on Ohm's law are very close. But, I did not want to overwhelm the intended reader of this Instructable with Ohm's law. This Instructable is for the person who is a bit timid about even using a multi-meter.