Question

A typical AA size rechargeable NiMH battery can store 1100-2100 mAh of electric charge. The small print on the battery in your hand says 1390 mAh. Can you express this amount of electric charge using the usual coulomb units?

Answer 1

The electric charge, q (in coulomb units) = 5004 C

Given:

The charge stored as printed on NiMH battery, q = 1390 mAh

Solution:

To express the amount of electric charge printed on the battery in milli-ampere-hour (mAh) in coulomb, we will do simple conversion of milli amperes in ampere and hours in seconds:

1 mA =
`1* 10^(-3)`

1 hour =
`60* 60 = 3600 s`

Also, we know that the rate of flow of charge is electric current, I:

I =
`(q)/(t)`

⇒ q = [tex]I\times t[tex] (1)

where

q = electric charge

I = current

t = time taken for flow of current

Using eqn(1), we get:

q = [tex]1390\times 10^{-3}\times 60\times 60[tex]

q = 5004 A-s = 5004 C