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Today I had an exam on Technology, and there was a question:

If a nano robot has a battery of 2.15Ah(Amper per hour) , how much it will last without recharching , if the robot spends 1.8I(Ampere) in continuity. Solve that on minutes!!

I did it this way, 2.15A*60Min/1.8A = 71 min , Am I right?

Thank you so much!

Michel Keijzers
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    yes but change your thinking "Amper per hour " to amps times hours or ampere-hour or Amp-hour or Ah – Tony Stewart EE75 Feb 28 '18 at 15:10
  • If you're ever trying to solve a real-world problem, you should be aware that the voltage declines while a battery discharges. That's important because, while batteries are rated in _charge_ capacity (i.e., Ampere-hours), the designer usually is interested in _energy_ capacity (Watt-hours). Converting from Ah to Wh is not as simple as multiplying by the voltage when the voltage does not remain constant. – Solomon Slow Feb 28 '18 at 15:47
  • FYI, when you say "intensity" I think the usual English term is *current*. (I think Romance languages often use some cognate of *intensity* for this word) – The Photon Feb 28 '18 at 17:00
  • that should be `1.8A`, not `1.8I` .... there is no unit of measurement that uses `I` ... who wrote the exam? – jsotola Feb 28 '18 at 17:47

1 Answers1

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Ah means ampere-hour, not ampere per hour (otherwise the battery would last forever).

But your calculation is correct, the battery has enough capacity for delivering 2.15 ampere (for one hour), so if your robot uses 1.8 A, it lasts for 2.15 Ah / 1.8 A = 1.19 hours, which is 1.19 * 60 = 71.6 minutes.

Transistor
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Michel Keijzers
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