2. (a) Which of these symbols is used to represent a thermistor in an electrical circuit? A B C D (b) A student investigates how the current in a lamp changes with the potential difference across the lamp - Edexcel - GCSE Physics Combined Science - Question 2 - 2019 - Paper 1

To calculate the missing resistance value, we use Ohm's Law, which states that:

$V = I \times R$

Where:

• $V$ is the potential difference in volts,
• $I$ is the current in amps,
• $R$ is the resistance in ohms.

We can rearrange the equation to find resistance:

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

Using the given data for when the potential difference is 5.0 V and the current is 0.26 A:

$R = \frac{5.0}{0.26} \approx 19.23 \Omega$

Since the table shows a resistance of 20 Ω for a potential difference of 6.0 V and a current of 0.30 A, we note that the value of resistance corresponding to potential differences of 4.0 V and 5.0 V falls within the expected range.