Question

The values of mA and uA are
(A) 10-6 A and 10-9 A respectively
(B) 10-3 A and 10-6 A respectively
(C) 10-3 A and 10-9 A respectively
(D) 10-6 A and 10-3 A respectively
8.
A cylindrical conductor of length V and uniform area of cross-section ‘A’
has resistance 'R'. Another conductor of length 2.5 l and resistance 0-5 R
of the same material has area of cross-section
(A) 5A
(B) 2.5 A
(C)
0-5 A
(D)
1
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Answer 1

Thus the value of area of cross section is A' = 5 A

Option (A) is correct.

Explanation:

We are given that:

• Length of conductor = V
• Area of cross section = A
• Resistance = R
• Length of conductor = 2.5 m
• Resistance = 0.5 R

Solution:

Formula of resistance is R = p L / A

Now if R' = 0.5 R

L' = 2.5 L

Then A' will be

0.5 R = p 2.5 L / A'

A' = 5 A

Thus the value of area of cross section is A' = 5 A

Answer 2

A' = 5 A

Explanation:

Given:

Length of conductor = L

Area of cross section = A

Resistance = R

Second conductor of same material length L' = 2.5L

Second conductor of same material resistance R' = 0.5R

Find: Cross sectional area of second conductor, A'.

Solution:

We know that resistance can be found using the formula:

R = p L / A

Where A is the cross-sectional area, R is the resistance, L is the length and p is the resistivity of conductor.

p will be the same for both the conductors as they are made of the same material as given.

So substituting the values, we get:

0.5 R = p 2.5L / A'

A' = 2.5/0.5 R

A' = 5 A

Area of cross-section of the second conductor is five times the area of cross section of the first conductor.