Test: Ohm's Law (NCERT) - NEET MCQ

The electrical resistance of a conductor is depend upon all factors i.e., size, temperature and geometry of conductor.

The slope of V-I graph gives the resistance of a conductor at a given temperature.

From the graph, it follows that resistance of a conductor at temperature T₁ is greater than at temperature T₂. As the resistance of a conductor is more at higher temperature and less at lower temperature.
Hence T₁ >T₂.

Let n be the number of turns in the coil. Then total length of wire used,
l = 2πr × n = 2π × 7 × 10⁻² × n
Total resistance, R = 
or 4 = 
∴ n = 70

The resistance of rod before reformation

Now the rod is reformed such that

∴   ( ∴ Volume remains constant)
or 
Now the resistance of the rod after reformation

∴ 
or   (using (i))
∴ R2 = R/4

If the wire is stretched by (1/10)^th of its original length then the new length of wire become

As the volume of wire remains constant then
⇒ 
Now the resistance of stretched wire.

=  
∴ 
= 18.15Ω