Question

Which of the following substances offer very low resistance?
$(A)$ nichrome
$(B)$water
$(C)$graphite
$(D)$steel

Answer 1

Hint: Electrical conductance means the ability of the substances to offer the free flow of electrons when the potential voltage is applied across them. Electrical Resistance is nothing but the opposite of electrical conductance. The SI unit of Electrical conductance is called $mho$and the SI unit of electrical resistance is called $ohm\left( \Omega \right)$. we need to compare nichrome, water, graphite, and steel with their resistive property and to find which has lower resistance than other substances.

Complete step by step answer:
When the voltage is applied across the substance there will be current passing through it. Ohm’s law states that” the voltage across the substance is directly proportional to current passing through it”.
$V \propto I$
$V = IR$
$R = \dfrac{V}{I}$
Where $V$-applied voltage
$I$-current
$R$-proportionality constant
That proportionality constant is known as the Resistance. The electrical resistance of the material depends on materials types, sizes, shapes. It is also affected by temperature. In different metallic substances, some free electrons are moving randomly in the atomic structure. Resistance of a material decreases when the number of free electrons increases.
From the above substances given on the question, Steel mainly has the composition iron and carbon have a less electrical resistivity of $1 \times {10^{ - 7}}$ ohm-meter at $20^\circ C$.
So that the steel offers very low resistance when compared to the other substances given. Steel has a large number of free electrons.

So, the correct answer is “Option D”.

Note: When compared to nichrome, water, and graphite, steel offers low resistance. Electrical resistivities of nichrome, water, graphite are $1.1 \times {10^{ - 6}}$ ohm-meter, ($2 \times {10^1}$ to $2 \times {10^3}$) ohm-meter, $1 \times {10^{ - 5}}$ ohm-meter respectively. Electrical Resistivity is the important property of a material that defines how strongly that the material resists electric current passing through it. The SI unit of Electrical Resistivity is called ohm-meter$\left( {\Omega .m} \right)$.