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A student connects a filament bulb to a battery - Edexcel - A-Level Physics - Question 14 - 2023 - Paper 1
Question 14
A student connects a filament bulb to a battery. The battery has internal resistance. The student connects an identical bulb in parallel with the first bulb, as sho... show full transcript
Worked Solution & Example Answer:A student connects a filament bulb to a battery - Edexcel - A-Level Physics - Question 14 - 2023 - Paper 1
Step 1
The resistance of the circuit decreases (as more bulbs are added)
Answer
When identical bulbs are connected in parallel, the overall resistance of the circuit decreases. This is due to the formula for total resistance in parallel circuits given by:
As more bulbs are added, the total resistance becomes smaller, which would typically lead to an increase in current.
Step 2
So there are more paths for the current (as more bulbs are added)
Answer
Each additional bulb provides a new path for the electric current. Therefore, even though the overall resistance drops, each individual bulb still receives less current due to the reduction in voltage across each bulb, which can lead to them dimming.
Step 3
So current in battery increases
Answer
As the total resistance decreases, according to Ohm's Law (), the overall current drawn from the battery increases. Thus, the increased current flowing through the internal resistance of the battery results in increased energy loss inside the battery.
Step 4
Terminal p.d. of battery decreases as bulbs get dimmer
Answer
In a circuit with internal resistance, as the load increases (more bulbs connected), the terminal potential difference (p.d.) of the battery decreases. This occurs because the internal resistance of the battery opposes the flow of current, leading to a decrease in voltage available to the bulbs, causing them to dim.
Step 5
So thermal energy increases in battery
Answer
With increased current flow due to the decreased resistance, more power is dissipated as heat within the battery, resulting in an increase in temperature. The internal resistance generates thermal energy, which raises the battery's temperature.