For a fixed conductor at a fixed temperature, which of the following is not the mathematical statement of Ohm’s law?( V = potential difference, I = current, E = electric field, J = current density, = resistivity, = conductivity, l = length of conductor, A = area of conductor) *
(a) V ∝ I
(b) E = J ρ
(c) J = σ E
(d) R = ρ l/A
Answers
Answer:
may be the answer is C.
Explanation:
A.because voltage is directly proportional to current and resistance is inversely proportional to current .
D. R=p l/A we know by the relation that the resistance of conductor is inversely proportional to the area of cross section.
E=Jp is not the statement for Ohm's law.
where E= electric field
J= current density
p = conductivity
All the three statements are correct:
- V=IR is the formula for Ohm's law which is shows the relationship between current, voltage and resistance. this law is one of the most basic laws and helps to calculate many other quantities such as, power, efficiency, voltage, current and resistance. Therefore this statement is correct.
- From Ohm's law:
I=V/R
since J=I/A = V/RA
=El / ((pl/A)*A)
= El/pl
= E/p
= σ E
Hence J = σ E, therefore this statement is also correct.
- For a wire of uniform cross-section, the resistance depends on its length l and the area A of cross-section.
R= pl/A
where p is the specific resistivity of the material. Therefore, this statement is also correct.
Therefore option b i.e. E = Jp is not the correct mathematical statement for Ohm's law.