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 find the missing resistance value, we can use Ohm's Law, which states that resistance (R) is equal to the potential difference (V) divided by the current (I):

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

From the table,

• For a potential difference of 6.0 V and a current of 0.30 A, we can calculate the resistance:

$R = \frac{6.0 \text{ V}}{0.30 \text{ A}} = 20 \text{ Ω}$

The resistance values appear constant for increases in potential difference, reinforcing that the lamp behaves in a predictable manner, where the resistance does not double when the potential difference doubles.