It's Tech Tuesday Time!!! (yes, it's already Tuesday in Australia) Today we are getting nerdy about electrons, current draw and resistance. To be more precise, we are discussing why choosing the right wire gauge is important and why an incorrectly sized wire correctly gets hot. We also go through the governing rules that dictate how much current a circuit is going to draw. . Got a question you want us to answer in the next Tech Tuesday? Leave it in the comments section!
Great video, as usual! I do think you could have also introduced the power equation P=VI in this video and how it easily works alongside Ohm's law to sort of 'close the loop'. A lightbulb is possibly the simplest way to demonstrate the relationship between P, V, I and the actual R of the hot filament. keep up the great work. 🙂
I see mention has been made of the P=VI, one aspect of this is it is possible to assess the heating of the wiring from the voltage drop times the current. one thing that seems to have been missed, and could have been introduced witht he fuel pump wiring, is the voltage drop through the wiring has a direct affect on the voltage, and current, at the pump - in this instance. As P=V²/R, the power loss is dis-proportional to the voltage at the pump - a 20% drop will mean the pump can only supply 64% of the nominal power to give the pressure/flow it should be able to supply - assuming a constant impedance (resistance) in the pump... On that, some types of electric motors will demand higher currents because they have lower impedance when operating below design voltages and/or speeds, which can rapidly lead to wiring or pump burn-out. On motors, while sometimes one can get away with sizing wiring to the current expected, there are times where minimising voltage drop is more important, such as with starter motors - you REALLY need to look at voltage drops there.
@Matt Wright Could be worth looking at stall and slow start loads and current control, and the use of fast and slow blow circuit breakers and switching? Been around 30 years, so a bit fuzzy with copper and iron losses/impedances.
Electrical flow to electronic different pressure. Available voltage to avaiable current flow the head of pressure ( voltage) to the flow of electrons past one point in one second (amps).
Lots of words, yes, but there is a lot of science that goes into the design and engineering of a car. It means that if you are building something yourself or modifying your car, you have to be across the science of it so you know when and why you should run new wiring for a fuel pump rather than use existing factory wiring, for example. It's all good content
@@haltech Great video. I’m interested in ecu failure mechanisms. Voltage spikes from faulty/incorrect relays generating say 400 volt back emf into the ecu, or too much current due a faulty earth . I’m assuming that’s in an activator, but why a fuse would not prevent that is beyond me. Thanks.
10:05, Electrons move through wire very, very slowly (and not the speed of lightning). Assuming 1.5A with 1mm² wire width, electrons are moving at about 40cm per hour, or 6.6mm per minute (this is electron drift). The speed of lightning (ignoring the vague description) will be measured in 1000s of km per second.
I think you are WRONG - If that indicator bulb draws 13.8 AMPS - That makes it a 190W bulb (W=AxV) - I think you are MISTAKEN. Indicator bulbs are usually 20W Even Main Headlamps are ONLY 55W You need to recheck this....
One must respect that a cold tungsten filament. They are a ptc . The higher temperature the filament is higher the resistance inital inrush current to operational current. Place a tungsten filament globe with a current clamp will give an inrush load of 180w. It's operational load is 21w at 12.8v. A cold tungsten filament is almost (/) resistance.
@@aaronfischer7199 I will accept your comment in good faith - BUT - If this is the case, then the wiring required is still NOT "13.8" AMP - is it? I have NEVER seen a wiring loom to an indicator that was HEAVY enough to run 13.8 AMPS? This is Incorrect. In summary - The advice is still Incorrect. The wiring for a 21 Watt bulb is covered by a 2 AMP cable - NOT a 13.8 AMP cable. This is a FACT - as can be seen if you look inside the light fitting on ANY car... REALITY is what we are concerned with here - Obviously car manufacturers are NOT allowed to under rate cables by law. Hence the low current loom to the indicators is 100% Correct and Safe. Cheers for the info 🙂
I think you didn't get what he showed in the video. Yeah the P part is missing but he showed with the Amp meter that there aren't 13.8 amps as he calculatet and he explaint why not.
@@tschui111 I'll take your word - I will leave this as a good faith initial "confusion" that they explained later - to be most charitable. Thanks for the info 🙂
@@mxwtubemxw The Amp rating of wire is for constant load (probably for less than ideal conditions, with a buffer), wire and most electronics can withstand much larger current for a short time. The bulb may draw 13.8 amps for 1/10 of a second and would not affect a wire (especially if it is a 10 amp wire). As an example, having just checked the data sheet of the first 1 ohm resistor in search results, it can withstand 2.5x voltage for 5 second without damage. Actual wire ratings 18 AWG is good for 10A at 60c, will fuse given 83A for about 10 seconds, or 250A for 1 second, or 1.4kA for 32ms Therefore a 10A wire will have no trouble handling the 13.8A for the time the globe takes to heat up (and increase it's resistance).
