actually that's backwards it's the voltage you really have to watch. Wattage is only a maximum capacity. watts is equal to volts multiplied by amps. If the voltage is the same and one supply can source 1 amp and another can source 2 amps, the second one will have a capacity twice that of the first. that is why you can use a higher watage supply on a computer that only requires a lower rating, as long as the voltage is exactly the same. using a lower wattage supply can destroy the supply if the computer requires more current than the supply is designed to produce. look at it like this. If you have one container with 10 gallons of water and a second with 50 gallons of water, you can dip a small cup into either one, but a bucket won't fit in the smaller container., because the larger bucket requires more water at once, but the cup requires a smaller ammount of water it can take it from either source.
it's also like aaa vs d size batteries. both are 1.5 volts, but the d size batteries have a mugh higher current capacity, you could say wattage capacity. a transistor radio could be powered by both the aaa or the d size batteries, but a huge boom box couldn't run from the aaa batteries because it requires more wattage or more correctly more current than the aaa batteries are capable of, and would deplete the aaa batteries almost instantly. if they were power supplies the aaa batteries would overheat and be destroyed while the d batteries could run the little transistor radio for months, because the transistor radio requires much less wattage or more correctly current. I hope that helps make it easier to understand why people tend to confuse volts ams and watts. if you would like to find the wattage of any power supply multiply it's voltage by it's current capacity, given in amp or miliamp ratings. most wall wart type supplies will say something like 5 volts dc or 5vdc 500ma output so 5 volts times .5 amps equals 2.5 watts. something you might see in a cell phone usb charger. and the big take away from this really should be, unless you want to carry a voltage and current meter, I'd just bring your own power supply. Besides sharing is a pain! Michael On Mar 16, 2011, at 12:01 PM, TIM KILBURN wrote: > Hi donna, > > You'll need to determine if the older charger has the same wattage output. > That is, is it a 60 watt or 85 watt unit. Typically, if your computer uses > the 85 watt power adapter, then as long as the other is the same wattage or > less, you'll be fine. The problems occur if you go the opposite direction, > that is, if your MBP uses the 60 watt power adapter, you cannot use the 85 > watt one as it can burn out components in the charging system. The wattage > rating is labeled on the charger itself as well as you should be able to find > this info on the web or within your electronic User's Guide. > > HTH. > > Later... > > > Tim Kilburn > Fort McMurray, AB Canada > > ----- Original Message ----- > From: Donna Goodin <goodi...@msu.edu> > Date: Wednesday, March 16, 2011 4:15 am > Subject: using older charger on my MB pro? > To: macvisionaries@googlegroups.com > > > Hi all, > > > > I'm going to be traveling the next few days, and will be staying > > with someone who has an MB pro that's about two-three years > > older than mine, i.e about 4-5 years old. Is there any > > reason I can't use her charger on my Macbook? > > TIA, > > Donna > > > > -- > > You received this message because you are subscribed to the > > Google Groups "MacVisionaries" group. > > To post to this group, send email to macvisionaries@googlegroups.com. > > To unsubscribe from this group, send email to > > macvisionaries+unsubscr...@googlegroups.com.for more options, > > visit this group at > > http://groups.google.com/group/macvisionaries?hl=en. > > > > -- > You received this message because you are subscribed to the Google Groups > "MacVisionaries" group. > To post to this group, send email to macvisionaries@googlegroups.com. > To unsubscribe from this group, send email to > macvisionaries+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/macvisionaries?hl=en. -- You received this message because you are subscribed to the Google Groups "MacVisionaries" group. To post to this group, send email to macvisionaries@googlegroups.com. To unsubscribe from this group, send email to macvisionaries+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/macvisionaries?hl=en.
