Another current question

[waynehoskins]

Always read the question which states a extension cord plugged in to a 120 volt receptacle, hence my super conductor question

Fair enough. I skipped reading the "extension cord" part when I did the numbers. But if the cable were quite short and of sufficient size to be of negligible resistance, it shouldn't have much voltage drop across it, allowing us to get pretty much 120 volts at the lamp terminals.

Since I enjoy figuring this stuff out, that means I'm a geek, right?

 

[David Ashton]

yes you're a geek but as you determined that the current is less than 5.2 and the question leaves open the cable resistance, you have to find that the only possible correct answers are a or b.Always answer the question, not the one they should ask, the one they did ask.

 

[Chris15]

In the words of one of my teachers, ATBQ... Answer The (Blood covered) Question.

If we're going to be good little geeks, we must also consider the capacitance and inductance of the cable, not just the straight DC resistance...

 

[David Ashton]

You can forget capacitance and inductance in this type of example, at 50 or 60hz the impedance of power cables is so close to the resistance as to be negligible, it becomes a real issue at and above audio frequencies.In this example the higher filament temperature would give a measurable increase in resistance where the capacitive and inductive effects would be unmeasurable.