Conduction of heat in rod is given by relation
where, K = coefficient of thermal conductivity of heat,
A = cross - sectional area,
∆θ = temperature difference,
t = time takn by heat flow
and l = length of rod.
If the radius of rod be r, then
A=πr2⇒Q= Rate of flow of heat through conductor,
= Here,
K,πand∆θ are constants.
∴
Q∝ For more value of Q,
(i) r should be maximum.
(ii) l should be minimum.
The value of
() for each observation,
(a)
r=1cm=10−2m,l=1m Q1∝==10−4 (b)
r=2cm=2×10−2m,l=2m Q2∝==2×10−4 (c)
r=1cm=10−2m,l=cm=×10−2m Q3∝==2×10−2 (d)
r=2cm=2×10−2m,l=m Q4∝==8×10−4 The value of
is maximum for the dimensions given in option (c), hence it will conduct maximum heat.