A student investigated how the resistance of a piece of wire varies with its length - AQA - GCSE Physics Combined Science - Question 3 - 2020 - Paper 1

To calculate X, we can use the formula for resistance, which relates voltage (V) and current (I). Using the measured values, we know that R = V/I and from the mean voltage, we find:

$X = 0.18 \, V$.

The relationship observed is that the resistance of the wire is directly proportional to its length. As the length of the wire increases, the resistance also increases. This correlation suggests that longer wires provide greater opposition to the flow of electric current, which is characteristic of conductive materials.

To find the current (I) in the blood sample, we can use Ohm's law where $I = \frac{V}{R}$. Given V = 0.90 volts and R = 7.5 ohms,

$I = \frac{0.90}{7.5} = 0.12 \, A$.

Using a new tube each time is critical, as variations in tube size, shape, or material could influence the resistance readings. To ensure consistent results that accurately reflect glucose concentration, it is essential to control these variables and maintain identical conditions across all tests.