A laboratory has purchased a new piece of equipment that has a high current demand. In the initial setup of the equipment, their extension cord caught fire due to an overly high current. Which of the following changes in the power cord would allow it to carry a larger current?
I. Increase the length of the power cord.
II. Increase the diameter of the power cord.
III. Use a material for the power cord that has a lower resistivity.
A. I and II only
B. I and III only
C. II and III only
D. III only
Click for Explanation
C is the correct answer. This question is really testing resistance. To carry a larger current, we want an extension cord with a smaller resistance. The equation to apply here is R = ⍴L/A where ⍴ is the resistivity, L is the length, and A is the cross sectional area. To lower resistance, we can decrease the resistivity, decrease the length, or increase the cross sectional area. Roman numerals II and III are consistent with these changes.
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