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A student plans to find the resistance of a nichrome wire with two different methods. The first method involves measuring the wire’s length ($l$) and diameter ($d$), then referencing the resistivity $\rho$ of nichrome.

The student uses $R=\cfrac { \rho l }{ \pi { (\frac { d }{ 2 } ) }^{ 2 } }$ to calculate the nichrome wire’s resistance.

The second method involves using alligator clips to connect the nichrome wire into a circuit with a 1.5-volt D-cell battery.

The student inserts an ammeter into the circuit to measure current $I$ and uses $R=\frac { \Delta V }{ I }$ to calculate the resistance.

The student wishes to conduct the second method properly. Of the choices below, which are the two most important actions to control in the experiment?

A

Make sure the nichrome wire is as straight as possible, not having any curves to it.

B

Collect the measurements quickly so that the nichrome wire does not have time to increase in temperature.

C

Set the nichrome on a hard metallic surface to ensure good conduction while taking measurements.

D

Connect the alligator clips to the very ends of the nichrome wire, not at points near the middle of the wire.

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