Subelement I: Power Sources— Topic 61: Batteries-2
Question 3-61I4
Element 3 (GROL)If a marine radiotelephone receiver uses 75 watts of power and a transmitter uses 325 watts, how long can they both operate before discharging a 50 ampere-hour 12 volt battery?
Explanation
To determine how long the battery can operate, first calculate the total power consumption. The receiver uses 75 watts and the transmitter uses 325 watts, for a combined total of 75 W + 325 W = 400 W.
Next, calculate the total current drawn from the 12-volt battery using the formula P = V * I, which means I = P / V.
I = 400 W / 12 V = 33.33 Amperes.
Finally, determine the operating time by dividing the battery's capacity in Ampere-hours by the current draw in Amperes.
Time = Battery Capacity / Current = 50 Ah / 33.33 A = 1.5 hours.
Therefore, the battery can operate both devices for 1.5 hours, or 1 hour and 30 minutes, before discharging.
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