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If we decrease the length of filament of a heater will it's area change?. In some cases I have seen that we change the area changes when the length changes to keep volume constant but in some cases we do not. Please tell me when we can do this and when we can't.

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  • $\begingroup$ @David Z , please see if the edit I've made makes the question clearer. $\endgroup$ Jul 6 '17 at 7:51
  • $\begingroup$ @TausifHossain It does make the question clearer, but it doesn't invalidate the reasons why I put it on hold. $\endgroup$
    – David Z
    Jul 6 '17 at 19:47
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It should be given at first if the volume remains constant which results in other changes not the other way around. For a metal wire that is usually the case that volume remains constant as it's very incompressible. Now, as $V=l*A$ if the length is increased and as volume remains constant the area must decrease. So as resistance is given by: $$R=\frac{{\rho}l}{A}$$ So as length is increased and Area is decreased so the resistance of the wire increases.

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