Equipment

1. Strip of foil
2. $50~\text{cm}$ ruler
3. Adjustable power supply
4. Two pairs of banana-alligator wires
5. Mutlimeter

In this problem we will study how well Ohm's law describes the experimental data for aluminium foil.

Consider an aluminium strip of length is $L$, width is $w$ and thickness $t$. When a voltage $U$ is applied across the ends of the strip the current $I=U/R$ flows through it, where $R$ is the resistance, which depends on the geometry of the strip and the material it is made of. The relation between resistance and dimensions of the strip is given by
\[R = \rho \frac{L}{wt},\]where $\rho$ is the resistivity of aluminium.

A1 For 11 different values of current $I$ flowing through the strip, measure the voltage drop $U$ across its ends.

Use a multimeter to measure a voltage. Use the reading from the adjustable power supply to measure the current. The maximum value of current should be less than $6~\text{A}$.

Attach the alligator clips only to the folded ends of the strip to avoid damaging it.

A2 Plot the graph $I$ vs $U$.

Now let's change the effective length of the strip. We will fix the current flowing through the strip at $I \approx6~\text{A}$ .

A3 Write down a chosen value of current $I$.

A4 Measure the dependse of the voltmeter reading $U$ on the length $L$. Perform 9 measurments.

Α5 Plot the graph of $U$ vs $L$.

The resistivity of the aluminium foil is $\rho = 2.9 \cdot 10^{-8}~\Omega \cdot \text{m}$.

A6 Determine the thickness of the foil $t$.