E2: Ohm’s Law — B level

What are we learning in this activity?

Choose one of these ways to learn about factors that affect resistance

Read Video

Resistance of a conductor depends on these four things:

Length of the conductor.
A longer conductor has more resistance.
Cross-sectional area of the conductor.
A thicker conductor has less resistance.
Resistivity of the material the conductor is made of.
Different materials conduct more easily or less easily.
Temperature.
Hotter conductors have more resistance than cool ones.

Questions

Answer these questions. Show any working you do, and give reasons for your answer.

Joey has extensions cords. They are both made of copper. The wires are the same thickness. But the red cord is 10m long and the yellow cord is 30m long. Which cord has more resistance?
Carla needs to replace the cable on her bore pump, because water got into it. She has two options: a cable with cross-sectional area of 1.5mm², and a cable with a cross-sectional area of 2.5mm². Which cable is going to have less resistance to let more volts get to the pump?
Incandescent lamps often have filaments (the glowing part) made of tungsten. The tungsten gets very hot - often 2000 or 3000 degrees. How does the resistance of the filament change when the lamp is turned on, compared to when it is off?
Essential Energy puts up high voltage power lines. They could put up copper or aluminium cables. Copper has lower resistivity than aluminium, so it conducts better. But copper costs a lot more than aluminium, and it is a lot heavier, so Essential Energy uses aluminium a lot of the time.
Would they use aluminium cables that have the same cross-sectional area as the copper option, or would they use thicker cables when using aluminium?