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Next##### Electricity

Question:

A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R′, then the ratio R/R′ is –

(a) 1/25 (b) 1/5 (c) 5 (d) 25

Answer:

We know,

It is given in the question that wire is divided into five equal parts, so after division, the area of cross-section(A) and resistivity(ρ) of the wire does not change only the length of wire will change.

Therefore, the resistance of wire

After division, the length of each part becomes .

So, the resistance of each part is .

The equivalent resistance of five parts in parallel combination:

So, the correct option is (d).

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