Why is my T61p power adapter only 2 prong?

Well, I was with my friend and he had his 4 year old Dell laptop with a 3 prong power adapter and he asked me the valid question as to why mine only had 2. Shouldn't a 3 prong(grounded) plug be standard? Have others thought about this point? What do you feel?

 

I think of two pronged as better because some outlets only are two prongers.

 

What about the lack of grounding? Every time I plug my adapter into my Surge protector I see a small spark.

 

Never had a problem with it.

 

in the US, neutral is connected to ground anyway so there's no need for a second ground.   ask your local electrician about it.

 

Ok, so its not a concern from what you are saying.

 

not a concern at all.   besides, i wouldn't be surprised if the 3-prong a/c adapter your friend's dell has is grounded to both earth and neutral at the a/c end of of the transformer.   unlike a/c (which can have neutral and earth grounds), d/c only has one ground.   eventually even a 3-prong adapter can only truly only have two prongs (so to speak).

earth grounds are nice but cannot substitute a good surge suppressor.   and, if your a/c adapter is going to fail then an earth ground won't help there, either.

having only two prongs isn't a bad thing and nothing to be ashamed of.

 

If you've ever had a notebook with a 3 prong adapter in a house/hotel/etc. with 2 prong outlets you will understand why 2 prong is standard on Thinkpads. 2 prong adapters also tend to be smaller than 3 prong adapters (helps with travel).

I have never had (nor heard of) a problem due to the 2 prong adapter on my x200 or older T40. However, there were dozens of times when the 2 prong adapter allowed me to actually use my laptop, and I am grateful for it.

 

Now this brings back some thread memories. I think a while back I had read that with Dell's XPS line some people were actually getting shocked by their machines and the solution that Dell had was to give them a 3 prong adapter, if I remember correctly.

Also on a side note, why do I get a small white/bluish spark when I plug in my Thinkpad adapter into my APC surge protector? The only things that are plugged into the surge protector are my Tv, DVD player and my Playstation(off when using laptop)?

 

Not sure, but I always plug my AC adapter into the wall BEFORE plugging it into my laptop and I don't get a spark.

 

Reminds me of a question I always wanted to ask: what about those car adapters, i.e. converting 12V DC to 120V AC, the ground prong obviously is only connected to the car frame... which is isolated from the ground by the 4 rubber (isolating) tires! So, my question is, if the laptop is in the end not really grounded, is it safe to use a notebook in a car?

 

there's a capacitor inside the adapter that fills up when you plug it in.   with the adapter disconnected from the thinkpad, plug it in, unplug it, and plug it back in consecutively and you won't see a spark the second time.

 

the notebook is still grounded to the car.   earth ground only matters in the event of electrical discharge from a lightening storm.   chassis ground is still connected to the negative terminal of the battery and forms a complete ground circuit.   the 12V adapter is either internally fused or the socket in your car is fused so there's little risk of damage from a short.   if you short out something in your car and it damages your laptop as a result then you've probably done something so bad that your car would no longer function.

 

Remember, in the end, you car is DC.
So is your laptop. that "brick" in the power cord is an ac/dc converter.

Neither really cares about "earth" ground.

It's kind of silly really, you are going from DC to AC and right back to DC. Pretty inefficient, energy loss w/ each transfer.

 

erik and all,
Thanks for the great info. So it looks like the 2 prong is both convenient and has adequate functionality. I thought the 3 prong was the best solution, looks like I was wrong. BTW - erik you should be an electrician, maybe you are I don't know

 

nope, just a graphic/industrial designer... but i do need to understand electronics, materials, thermodynamics, and manufacturing processes for my job.