Ncert Exercises & Solutions

A metal rod of length 10 cm and a rectangular cross-section of 1 cm x 1/2 cm is connected to a battery across opposite faces. The resistance will be:

1.	maximum when the battery is connected across 1 cm x 1/2 cm faces.
2.	maximum when the battery is connected across 10 cm x 1 cm faces.
3.	maximum when the battery is connected across 10 cm x 1/2 cm faces.
4.	same irrespective of the three faces.

(a) Hint: The resistance of the rod will depend on the dimensions of the rod.

Step 1:

The resistance of the wire is given by:

R = ρ \frac{l}{A}

Step 2:

For the greater value of R, l must be higher and A should be lower and it is possible only when the battery is connected across 1 cm x

(\frac{1}{2})

cm (area of cross-section A).