IB Physics SL B 5 6 Potential Difference and Electrical Energy Transfer Questions

Practise IB Physics SL B.5.6 by tracking electrical energy delivered, stored and recharged using voltage, current and time.

Exam points

Calculate the energy delivered by a cell with E=VIt, then use solar intensity, panel area and charging efficiency to determine the minimum recharge time.

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Study B.5.6—Potential difference and electrical energy transfer conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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A fully charged cell of emf 6.0 V delivers a constant current of 5.0 A for a time of 0.25 hour until it is completely discharged.

The cell is then re-charged by a rectangular solar panel of dimensions $0.40 \mathrm{~m} \times 0.15 \mathrm{~m}$ at a place where the maximum intensity of sunlight is $380 \mathrm{Wm}^{-2}$ .

The overall efficiency of the re-charging process is 18 %.
Calculate the minimum time required to re-charge the cell fully.

ALTERNATIVE 1

«energy output of the panel = » VIt OR $6 \times 5 \times 0.25 \times 3600$ OR 27000 «J»

«available power => $380 \times 0.4 \times 0.15 \times 0.18$ OR 4.1 «W»

$t=\ll \frac{27000}{4.1}=>6600<\mathrm{S} \gg$

ALTERNATIVE 2

«energy needed from Sun = » $\frac{V I t}{\text { eff }}$ OR $\frac{6 \times 5 \times 0.25 \times 3600}{0.18}$ OR 150000 «J»

« incident power=» $380 \times 0.4 \times 0.15$ OR 22.8 «W»

$t=\ll \frac{150000}{22.8}=>6600<\mathrm{S} \gg$

Marking guidance:

Allow ECF for MP3

Accept final answer in minutes (110) or hours (1.8).

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IB Physics SL B 5 6 Potential Difference and Electrical Energy Transfer Questions question 1