I'm currently studying the textbook Fundamentals of Electric Circuits, 7th edition, by Charles Alexander and Matthew Sadiku. Chapter 1.5 Power and Energy gives the following practice problem:
Practice Problem 1.6
A home electric heater draws 12 A when connected to a 115 V outlet. How much energy is consumed by the heater over a period of 24 hours?
The answer is said to be 33.12 k watt-hours.
The chapter says that the energy absorbed or supplied by an element from time \$t_0\$ to time \$t\$ is $$w = \int_{t_0}^t p \ dt = \int_{t_0}^t \nu i \ dt, \tag{1.9}$$
where \$ \nu \$ is the voltage, \$ i \$ is the current, and \$w\$ is energy in Joules. It then says that 1 Wh = 3,600 J.
So, by my calculation, we have
$$\int_0^{24} 12 \times 115 \ dt = \left[ 1380t \right]_0^{24} = 33120 \text{ J}.$$
But, converted to watt-hours, as in the textbook's answer, this would be \$ \dfrac{33120}{3600} = 9.2 \text{ Wh}\$. Am I misunderstanding something? Are my units incorrect? Or is this, perhaps, a textbook error?
quantity per second
toquantity per hour
... are you somehow confusing time intervals? \$\endgroup\$