Question

Resistance of a meatel wire of length 1 m is 26 ohm at 20 celcius . If the diameter of the wire is 0.3mm , what will be the resistivity of the meatel at that temperature? Using table 12.2, predict the material of the wire

Answer 1

heya....


Resistance , R = 26Ω 

Length of wire , L = 1m 

diameter of circular part of wire ,d = 0.3mm = 0.3 × 10⁻³m 

so, base area of wire , A = πr² = πd²/4 [ ∵d = 2r] 

= 3.14 × (0.3 × 10⁻³)²/4m²

= 3.14 × 9 × 10⁻⁸/4 m² 

= 28.26/4 × 10⁻⁸ m² = 7.06 × 10⁻⁸ m² 

Now, use formula, 

R = ρL/A 

Here, R is the resistance, ρ is the resistivity , L is the length of wire and A is the base area of it .

So , ρ = RA/L = 26Ω × 7.06 × 10⁻⁸m²/1m

ρ = 1.8356 × 10⁻⁶ Ωm 

Hence, resistivity is 1.8356 × 10⁻⁶ Ωm at 20°C


tysm.......@gozmit

Answer 2

solution

we know that.


resistive = AR/ l

Now, area of wire= 1m* 0.3mm

= 1000*0.3

= 300 mm^2

now,, putting value in formula.

=> resistivity= 300* 26/1000

= 26*3/ 10

= 7.8 ohm - mm

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hope it helps you. ☺☺