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Chapter 18: Problem 12

A solar cell provides an emf of \(0.45 \mathrm{V}\). (a) If the cell supplies a constant current of \(18.0 \mathrm{mA}\) for \(9.0 \mathrm{h},\) how much electric energy does it supply? (b) What is the power-the rate at which it supplies electric energy?

Short Answer

Expert verified
Question: A solar cell has an emf of 0.45 V and supplies a current of 18.0 mA for 9.0 hours. Calculate (a) the electric energy supplied by the solar cell and (b) the power supplied by the solar cell. Answer: a) The electric energy supplied by the cell is approximately 26.334 J. b) The power supplied by the solar cell is approximately 0.0081 W.

Step by step solution

01

a) Electric energy

To find the electric energy, we need to multiply the emf, current, and time. The emf is given as 0.45 V, the current as 18.0 mA, and the time as 9.0 h. Firstly, we will convert the current from mA to A and the time from hours to seconds: \(I = 18.0 \ \text{mA} = 18.0 \times 10^{-3} \ \text{A}\) \(t = 9.0 \ \text{h} = 9.0 \times 3600 \ \text{s}\) Now we can find the electric energy using the formula \(E = VIt\): \(E = (0.45 \ \text{V}) \times (18.0 \times 10^{-3} \ \text{A}) \times (9.0 \times 3600 \ \text{s})\) \(E \approx 26.334 \ \text{J}\) The electric energy supplied by the cell is approximately 26.334 J.
02

b) Power

To find the power, we need to multiply the emf and current. We have already converted the current to amperes. Using the formula \(P = VI\), we get: \(P = (0.45 \ \text{V}) \times (18.0 \times 10^{-3} \ \text{A})\) \(P \approx 0.0081 \ \text{W}\) The power supplied by the solar cell is approximately 0.0081 W.

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