# Amp question

1. Apr 10, 2004

### david90

How long will a device drawing 8 mA last on a 12 v bat that has a 25mAh?

25/8 = 3.125 hours?

2. Apr 10, 2004

### chroot

Staff Emeritus
You got it.

- Warren

3. Apr 10, 2004

### david90

is there a bat as small as a watch bat that can produce that much mAh at 12v?

4. Apr 10, 2004

### chroot

Staff Emeritus
Not that I know of.

- Warren

5. Apr 10, 2004

### david90

what is ur mAH for watch bat?

6. Apr 10, 2004

### chroot

Staff Emeritus
Hell if I know, but I've never seen a 12V watch battery. Most battery chemistries in use today are 1.5 volts or so -- they'd have to pack 8 cells into that watch battery package to get 12V, and I don't think it's been done.

- Warren

7. Apr 10, 2004

### hitssquad

8. Apr 10, 2004

### hitssquad

Electrical current and pressure

Voltage is electrical pressure, and it is analogous to water pressure. We don't need to know what the voltage is to answer this; we just need to know that it is considered consistent throughout the problem. The question should be stated as:How long will a device drawing 8 mA at a particular given voltage last on a battery that has a capacity of 25mAh at the same given voltage?.

Yes, if the question is stated as I corrected above.

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