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A student measures the terminal potential difference (V) of a cell (of emf $\varepsilon$ and internal resistance r) as a function of the current (I) flowing through it. The slope and intercept of the graph between V and I are then respectively equal to
A
$-\varepsilon$ and r
B
$\varepsilon$ and –r
C
–r and $\varepsilon$
D
r and $-\varepsilon$
Detailed Solution
Terminal potential difference of a cell supplying current I: $V = \varepsilon - Ir$
Rewrite as $V = (-r)I + \varepsilon$ and compare with the straight line $y = mx + c$, with V on the y-axis and I on the x-axis.
Slope m = –r
Intercept on the V-axis c = $\varepsilon$
Hence the slope and intercept are –r and $\varepsilon$ respectively.
Rewrite as $V = (-r)I + \varepsilon$ and compare with the straight line $y = mx + c$, with V on the y-axis and I on the x-axis.
Slope m = –r
Intercept on the V-axis c = $\varepsilon$
Hence the slope and intercept are –r and $\varepsilon$ respectively.