First slide

Ohm's law

Question

Dimensions of a block are 1 cm x 1 cm x 100 cm. If specific resistance of its material is $3 \times 10^{- 7}$ ohm-m, then the resistance between the opposite rectangular faces is

Easy

A

$3 \times 10^{- 9} o h m$
B

$3 \times 10^{- 7} o h m$
C

$3 \times 10^{- 5} o h m$
D

$3 \times 10^{- 3} o h m$

Solution

$L e n g t h l = 1 c m = 10^{- 2} m$
Area of cross-section A = 1 cm x 100 cm
$\begin{array}{l} = 100 c m^{2} = 10^{- 2} m^{2} \\ Re s i s \tan c e R = 3 \times 10^{- 7} \times \frac{10^{- 2}}{10^{- 2}} = 3 \times 10^{- 7} Ω \end{array}$

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