A 150Ω carbon resistor is connected across a dc power supply of unknown emf. During a 20s interval, 8.0J of electrical energy is transformed into thermal energy in the resistor. Assume the resistance remains constant.
(a) Determine the current in the resistor during the 20s interval.
(b) Determine the emf of the power supply.
(c) Calculate the rate at which energy is converted in the resistor during this interval.
(d) A second resistor made of the same carbon material has twice the length but the same cross-sectional area as the first resistor. It is connected across the same emf for 20s. Determine the energy it converts during that time and justify your answer.