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6. (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 6 - 2019 - Paper 1
Question 6
6. (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 ch... show full transcript
Worked Solution & Example Answer:6. (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 6 - 2019 - Paper 1
Step 1
Calculate the value of resistance that is missing from the table.
Answer
To find the missing resistance value, we can use Ohm's law, which states that:
where R is the resistance, V is the potential difference, and I is the current.
Referring to the table in Figure 9, we calculate the missing resistance for the potential difference of 5.0 V and current of 0.30 A:
Thus, the missing resistance is approximately 17 Ω.
Step 2
Comment on the student’s conclusion.
Answer
The student's conclusion states that the resistance of the lamp is directly proportional to the potential difference.
However, analyzing the data provided in Figure 9:
- As the potential difference increases from 1.0 V to 6.0 V (in increments of 1 V), the resistance does not increase linearly. For example, at 3.0 V the resistance is 17 Ω, while at 4.0 V it rises to 18 Ω and then to 20 Ω at 5.0 V.
- This indicates that resistance does increase with potential difference, but not in a simple proportional manner, suggesting that factors like temperature variation could also be influencing resistance.
Therefore, while the student’s observation captures a general trend, it is not entirely accurate since the relationship is not a straight line.
Step 3
Explain how energy is transferred from the battery, through the lamp, to the surroundings.
Answer
The battery converts chemical energy into electrical energy, which moves through the circuit to the lamp.
Here's how this process works:
- The battery contains chemical energy, which is released as the charged particles (electrons) flow from the negative terminal to the positive terminal.
- When the circuit is completed, electrons begin to flow through the filament of the lamp.
- As the electrons move, they collide with ions in the filament, transferring energy. This energy causes the lattice structure of the metal to vibrate more, increasing the temperature of the filament.
- The lamp emits light and heat as energy is dissipated to the surroundings.
- The increased temperature of the filament excites the atoms and emits light, demonstrating energy transfer in both thermal and electromagnetic forms.