A laboratory power supply provides a constant potential difference of

PHYSICS · Multi-part · CBSE · Physics · Current Electricity · Current Electricity

Problem

12.0\,\text{V}

. Three interchangeable sample cells can be inserted into a simple series circuit that also contains an ideal ammeter and a warning lamp that lights when the current exceeds

0.20\,\text{A}

. The three sealed sample cells are described below. Each cell has identical internal dimensions (path length =

4.0\,\text{cm}

, cross-sectional area =

1.5\,\text{cm}^2

) and stainless-steel electrodes. • Cell X is packed with a cylindrical rod of pure aluminum. • Cell Y is packed with a cylindrical pellet of solid lithium fluoride. • Cell Z is filled with molten lithium fluoride at

900\,^\circ\text{C}

. Measured resistances for the three cells at the operating temperature are given in the table.

Cell	Measured resistance ( $\Omega$ )
X	$0.45$
Y	$4.8 \times 10^5$
Z	$7.5$

(a) Calculate the current that flows when Cell X is inserted into the circuit. (b) Calculate the current when Cell Y is inserted. (c) Calculate the current when Cell Z is inserted. (d) For which of the three cells will the warning lamp turn on? Justify your answer by referring to your calculations and the nature of mobile charge carriers in each sample.

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