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3. (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 - Question 3 - 2019 - Paper 1
Question 3
3. (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... show full transcript
Worked Solution & Example Answer:3. (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 - Question 3 - 2019 - Paper 1
Step 1
Calculate the missing value of resistance for potential difference 2.0 V
Answer
To calculate the resistance for the potential difference of 2.0 V, we use Ohm's law, which states:
Substituting the values from the table:
- For 2.0 V, the current is 0.14 A.
- Therefore, the resistance is:
However, the table shows intervals for resistance as whole numbers. The closest value, 14 Ω, might have been what was intended for the 2.0 V measurement.
Step 2
Discuss the relationship between potential difference and resistance
Answer
The resistance does increase with potential difference. However, it is essential to note that doubling the potential difference does not result in doubling the resistance. This can be seen from the changes in the current values from the table:
- For instance, moving from a potential difference of 2.0 V to 4.0 V (which doubles the potential difference) leads the current to increase from 0.14 A to 0.22 A, representing a resistance increase from 14 Ω to 18 Ω. This indicates that the increase in resistance is not proportional to the increase in potential difference.