Question

A 4–Ohm resistance wire is doubled up by folding. calculate the new resistance of the wire ​

Answer 1

Answer:

2-Ohm.

Explanation:

Resistance is inversely proportional to area and directly proportional to length.

So when length is halved and area is doubled, resistance is halved. So, 4/2 = 2 Ohm.

Now, your doubt will be that, why we took lenght halved when it is mentioned in question that wire is doubled. So, the answer is the length is not doubled. The wire is folded. So, area of cross-section is doubled and length is halved.

Answer 2

Answer

1 ohm

reason

resistivity = RA/L

hence (resistivity×L)/A = R

Explanation:

HERE WHEN FOLDED

LENGTH IS HALVED

• THEREFORE AREA OF CROSS SECTION

2π(R)square

which becomes twice

• resistivity remains the same
• 2πRsquare is the new area

hence the new resistance becomes

(resistivity × L/2)/(2 πRsquare)

• hence resistance = (resistivity × L)/( 4πRsquare)

new. resistance = old resistance /4

therefore new resistance 4/4

1 ohm

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