P = U ² / r

if U = u
P = p: The surface charge density (W / cm ²) is preserved
P = U ² / U ² re = / 2r
if U = u
P = p / 2: The surface charge density (W / cm ²) is divided by 4
P = U ² / re = 2.U ² / r
re = r / 2
si U = u
P = 2p: The surface charge density (W / cm ²) is preserved
P = 3.U ² / r
if U = u
P = 3p: The surface charge density (W/cm2) is preserved
if U = \ / ¯ 3u
P = 9p: The surface charge density (W/cm2) is multiplied by 3 (it may destroy the resistance)
if U = u / \ / ¯ 3
P = p: The surface charge density (W/cm2) is divided by 3
P = 3.U ² / r = U ² / r
if U = u \ / ¯ 3
P = 3p: The surface charge density (W/cm2) is preserved
if U = u
P = p: The surface charge density (W/cm2) is divided by 3
if U = u / \ / ¯ 3
P = p / 3: The surface charge density (W/cm2) is divided by 9
P = 3.U ² / re = U ² / re

P = 3.U ² / Re

Resistors r1, r2, ... rn in series
Resistors r1, r2, ... rn parallel
Re = r1 + r2 + ... + Rn
If r1 = r2 = ... = Rn = r Re = n.r
1 / Re = 1 / r1 + 1/r2 + ... 1 / rn
If r1 = r2 = ... Rn = r = 1 / Re = n.1 / r Re = r / n
NOTE: If p is the power of the heater at the rated voltage u and U the voltage, the total power P and the drying surface (W / cm ²) are equal to: