# Energy problem

1. Apr 17, 2005

### danne89

A battery is being charged by a voltage v=11+0.5t V and a constant current of 2 A. The price of a kWh is 10 cent. How much is 5 hours battery-charging?

My work:
p = 22 + t
$$w= \int_{0}^{5} x dt = 25/5 + 22*5 = 122.5 W$$
122.5 W in 5 h = 5 * 122.5 Wh = 0.6125 kWh

2. Apr 17, 2005

### Theelectricchild

$$w= \int_{0}^{5} p(t) dt$$

where p = VA = 22 + 1t correct?

Just integrate that from zero to five to get the power then do the last step... i think its correct.

you should end up getting 122.5 JOULES like you did... your answer is correct.

Just make sure your units are right.

Last edited: Apr 17, 2005
3. Apr 19, 2005

### danne89

I solved it. I did indeed just need to crack the units.

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