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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
Question 2
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... show full transcript
Worked Solution & Example Answer: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
Step 1
Calculate the missing resistance using Ohm's Law
Answer
To find the missing resistance, we can use Ohm's Law, which states that:
Where:
- is the resistance in ohms (Ω)
- is the potential difference in volts (V)
- is the current in amperes (A)
From the table, we know that for a potential difference of 6.0 V, the current is 0.30 A. Plugging these values into the formula gives:
Thus, the missing resistance value is 20 Ω.
Step 2
Describe the relationship between current, potential difference, and resistance
Answer
The student should comment that as the potential difference increases, the current generally increases as well, illustrating that resistance increases with potential difference. However, it is important to note that doubling the potential difference does not necessarily result in doubling the resistance, indicating a nonlinear relationship.
Step 3
Propose a circuit diagram modification to measure resistance
Answer
To measure resistance accurately, the student could use a variable resistor (rheostat) connected in series with the lamp and a power supply. This allows adjustments to the circuit to observe changes in current. Alternatively, a potential divider circuit could be employed, with components arranged in parallel across the power supply, creating a more stable voltage across the lamp for measurement.