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

Given the mean potential difference is calculated by averaging the measurements:

o diff erence = rac{1 + 3 + X}{3}

We also have the mean given as 0.17.

Setting up the equation:

0.17 = rac{4 + X}{3} \rightarrow 0.51 = 4 + X \rightarrow X = 0.18\ V

The resistance of the wire is directly proportional to its length. As the length of the wire increases, the resistance also increases. This is due to the fact that longer wires provide more opposition to the flow of electric current.

Using Ohm's Law, we know that:

$I = \frac{V}{R}$

where:

• V = 0.90 V (potential difference)
• R = 7.5 \Omega (resistance)

Plugging in our values:

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

Each blood sample is tested in a new tube to ensure that the dimensions and properties of the tubes do not vary. If the tubes differ in width or shape, they could affect the resistance measured by the glucometer, leading to inconsistent results. Therefore, maintaining identical conditions is crucial for valid comparisons.