Final answer:
The steady current that a 1.5 V D-size battery can provide for 20 hours before being depleted is 1 ampere (A).
Step-by-step explanation:
To find the steady current that the 1.5 V D-size battery can provide for 20 hours before being depleted, we need to calculate the total energy provided by the battery and then divide that by the time. The total energy is given as 72 kJ. We convert this to joules by multiplying by 1000 (1 kJ = 1000 J), so the total energy is 72,000 J.
Now, we divide the total energy by the time of 20 hours to find the steady current. Since current is the rate at which charge flows, we use the formula:
current = energy / time
Plugging in the values, we have:
current = 72,000 J / (20 hours x 3600 s/hour)
Simplifying the units, we get:
current = 72,000 J / 72,000 s
So, the steady current that the battery could provide for 20 hours before being depleted is 1 ampere (A).