How does the resistance of wire changes when-(a)
The Length is tripled.
(b) Its diameter is tripled.
Class 10
Answers
Answer:
1 Answer. Resistance becomes 1/9 th. Resistance becomes 3 times.
Explanation:
How does the resistance of a wire change when:
a) its length is tripled?
b) its diameter is tripled?
c) its material is changed to one whose resistivity is three times?
R = p. 1/A
(a) I → 3l
R’ = P. 3 l/A = 3 R
Resistance gets tripled,
(b) d → 3d
R = p. I/A = R = P. 1/ πr2 = P.1/π(d/2)2
R’ = P. I/π (3d/2)2 = (1/9)p. I/π(d/2)2 = R/9
Resistance becomes 1/9 th.
(c) R = P. I/A
P → 3P
R’ = 3p. I/A = 3R
Resistance becomes 3 times.
Answer. Resistance becomes 1/9 th. Resistance becomes 3 times.
R=ρ
A
l
(a) l→3l
R
′
=ρ
A
3l
=3R
Resistance gets tripled.
(b) d→3d
R=ρ
A
l
=R=ρ
πr
2
l
=ρ
π(d/2)
2
l
R
′
=ρ
π(3d/2)
2
l
=
9
1
ρ
π(d/2)
2
l
=
9
R
Resistance becomes
9
1
th.
(c) R=ρ
A
l
ρ→3p
R
′
=3ρ
A
l
=3R
Resistance becomes 3 times.
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