two wires of equal length made up of material of resistivity ratio 1 is to 2 and area ratio 3 is to 2 have the potential drop across them in the ratio X is to why in series the X to Y ratio is
a. 3:1
b. 2:5
c. 5:2
d. 1:3
plz give the answer with explanation
Answers
Given: Two wires of the same material having lengths in the ratio of 1:2 and diameters in the ratio of 2:3 are connected in series with an accumulator.
To find the ratio of the potential difference across the two wires.
Solution:
Let ρ be the resistivity of the material of the wire.
First wire:
Length = L
Diameter = 2d
Area of Cross-section, A = π(22d)2=πd2
Resistance, R=ρAL=ρπd2L
If current I flows through the combination then the potential difference across R is, V=IR
Second wire:
Length = 2L
Diameter = 3d
Area of Cross-section, A′=π(23d)2=49×πd2=49×A
Resistance, R′=ρA2L′=ρ49A2L=ρ9A8L=98ρAL=98R
If current I flows through the combination then the potential difference across R′ is, V′=IR′=98IR
So, the ratio of potential difference across the wires in series is,
V:V′=IR:98IR=9:8
Explanation:
Given: Two wires of the same material having lengths in the ratio of 1:2 and diameters in the ratio of 2:3 are connected in series with an accumulator.
To find the ratio of the potential difference across the two wires.
Solution:
Let ρ be the resistivity of the material of the wire.
First wire:
Length = L
Diameter = 2d
Area of Cross-section A= π( 2d/2)square=πdsquare
Resistance, R=ρ L/A= ρ L/πd square
If current I flows through the combination then the potential difference across R is, V=IR
Second wire:
Length = 2L
Diameter = 3d
Area of Cross-section, A'=π(3d/2)square=9/4xπd square=9/4xA
Resistance, R'=p 2L'/A=p 2L/9/4A=p 8L/9A=8/9p L/A=8/9R
If current I flows through the combination then the potential difference across R' is, V' =1R'=8/9IR
So, the ratio of potential difference across the wires in series is,
V:V' = IR:8/9IR=9:8
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