Accepted Answer
Resistance-1 = (voltage-1) / (current-1) = (12 V) / (0.185 A) = 64.9 ohms .Resistance-2 = (voltage-2) / (current-2) = (90 V ) / (1.25 A) = 72 ohms .The resistance changed between situation-1 and situation-2 .How did that happen ?Power = (voltage) x (current)Power-1 = (12) x (0.185) = 2.22 wattsPower-2 = (90) x (1.25) = 112.5 wattsThe poor resistor dissipated 51 times as much power during the second trial. It got all heated up, and its resistance went through the roof.Carbon resistors behave nicely and reliably, until you try totoast bread or light up your bedroom with them.