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NCERT Class XII Chapter
Current Electricity
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Question : 8 of 24
Marks: +1, -0
A heating element using nichrome connected to a 230 V supply draws an initial current of 3.2 A which settles after a few seconds to a steady value of 2.8 A. What is the steady temperature of the heating element if the room temperature is 27.0 °C ? Temperature coefficient of resistance of nichrome averaged over the temperature range involved is 1.70 × 10−4 ∘C−110^{-4}\,{}^{\circ}\mathrm{C}^{-1}.
Solution:  
At room temperature 27 °C, the resistance of the heating element.
R27∘R_{27^{\circ}} = 2303.2\frac{230}{3.2} = 71.875 Ω
At the steady temperature t °C , the resistance.
RtR_t = 2302.8\frac{230}{2.8} = 82.143 Ω
Now , R2R_2 = R1R_1 [1 + α (t2−t1)(t_2-t_1)]
or 82.143 = 71.875 [1 + 1.7 × 10−410^{-4} (t – 27)]
or 0.0840 × 10410^4 = t – 27 or 840 = t – 27 or t = 867 °C.
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