A watch battery can supply approximately 15 C of charge before it needs to be replaced. Calculate the number of hours it will last if the current drawn by the watch is 0.50 micro-amps
To calculate the number of hours a watch battery will last, you first need to convert the charge capacity from coulombs to amp-hours.
1 C (coulomb) is equal to 1 ampere-second. Since there are 3,600 seconds in an hour, we can convert the charge from coulombs to amp-hours using the formula:
Charge (in amp-hours) = Charge (in coulombs) / 3600
In this case, the charge capacity is 15 C. Converting it to amp-hours:
Charge (in amp-hours) = 15 C / 3600 = 0.00417 Ah
Now that we have the charge capacity in amp-hours, we can calculate the number of hours the battery will last by dividing the charge capacity by the current drawn by the watch.
The current drawn by the watch is given as 0.50 microamps. To convert it to amperes:
Current (in amperes) = Current (in microamps) / 1,000,000
Current (in amperes) = 0.50 μA / 1,000,000 = 0.00000050 A
Now we can calculate the number of hours:
Number of Hours = Charge (in amp-hours) / Current (in amperes)
Number of Hours = 0.00417 Ah / 0.00000050 A = 8,340 hours
Therefore, the watch battery will last approximately 8,340 hours if the current drawn by the watch is 0.50 microamps.