ei: i have an A/C adapter
listing input - 120v -60Hz-10w
output - 12v DC -0.5A
how many mAh = 0.5A ?
2007-06-19 07:49:03 · 7 answers · asked by roadriper1 2 in Science & Mathematics ➔ Engineering
.5 Amps = 500 mA. This is just the current flow.
mAh (Milliampere-hours) is a measure of battery capacity at a certain level of current. Example: A 12V, 2Ah battery could supply .5A for 4 hours (.5A x 4hr = 2Ah). Ampere-hours is a more common unit than Milliamp-hours.
The other answer is correct here, you don't need to consider hours. If the power supply is fed from the utility, it'll always be on.
2007-06-19 08:07:45 · answer #1 · answered by Dave O 3 · 0⤊ 0⤋
That's like asking, how many gallons of gasoline = 100 hp
It can't be answered because mAh and A are different things.
If e.g. a light bulb uses 0.5A and you switch it on for 1 hour the light bulb will have used up 0.5Ah. If you switch it on for 2 hours it will be 1Ah and so on.
1Ah = 1000mAh.
So if a battery has 2000mAh it could power the lamp for 4 hours.That is of course only if the voltage is right. So it has to be a 1.5V, 0.5A light bulb.
2007-06-19 15:04:59 · answer #2 · answered by Voice of Insanity 5 · 0⤊ 0⤋
Background:
.5A = 500 milliamps(mA). That rating means that the adapter is guaranteed to continue to supply 12V as long as you don't exceed 500 milliamps of current. It is safe to stay within/under the rated limits. If your application draws over 500mA, the voltage typically degrades.
As for you mAh question, it's easy to explain with examples.
1) If your application draws 100mA from the adapter and you leave it on for 1 hr, you have used energy at a rate of 100milliamp hours (mAh).
2) If your application draws the full 500mA from the adapter continuously for 1 hr, you have used energy at a rate of 500mA hours.
3) If your application draws the full 500mA from the adapter continuously for 30 min., you have still used energy at a rate of 500mA hours.
4) If your application draws 500mA from the adapter for 30 minutes out of a whole hour (half duty - half the time it is drawing 500mA and half the time it is off), for that whole hour you have used energy at a rate of 250mAh. However, your instantaneous energy use rate would be either 500mAh or 0mAh depending on where you sample.
Hopefully, that is as clear as mud. Just think of Amp Hours as a rate of energy usage.
2007-06-19 17:37:24 · answer #3 · answered by Nukey 1 · 0⤊ 0⤋
Unlimited
At least as long as the power stays on. An AC adapter is not a battery. A battery can put out a certain amount of current for a certain length of time before it dies. But an AC adapter can continue to put out its rated current for as long as the AC is provided to its input.
Just for the sake of completeness, 0.5A = 500 ma
2007-06-19 14:57:13 · answer #4 · answered by dogsafire 7 · 2⤊ 0⤋
Not sure what you are asking. The definition of Ah is:
"An ampere-hour (abbreviated as Ah or A-h) is a unit of electric charge. One ampere-hour is equal to 3600 coulombs (ampere-seconds), and is the amount of electric charge transferred by a steady current of one ampere for one hour."
So, after 1 hour, 0.5 A = 0.5 Ah = 500 mAh
2007-06-19 14:59:28 · answer #5 · answered by Randy G 7 · 0⤊ 0⤋
amperes is a unit of current while mAh is,in a certain way a unit of energy, because,if the voltage is held constant,multiplying
Ah by this voltage you get VAh = VA*3600 VA s which are in units of Joules.
So if you use your adapter for "n" hours you get an energy of
n*12*0.5*3600 joules
2007-06-19 15:07:28 · answer #6 · answered by santmann2002 7 · 0⤊ 0⤋
mAh is mili amp hours
one Ah = 1000 mAh, so 0.5 Ah = 500 mAh
An Amp hour is a current of one Amp for a period of one hour.
2007-06-19 15:00:34 · answer #7 · answered by Philip H 7 · 0⤊ 0⤋