1. James is given an unknown number of identical bulbs and a 10-V battery. When he connects them in series to the battery, the current through the battery is 0.01 A. When he connects the bulbs in parallel, the current through the battery is 1 A. Find the number of bulbs. (4 marks)
The answer is 10.
一條關於Electric Circuit的簡單物理問題
2009-11-09 7:19 am
回答 (1)
2009-11-09 7:38 pm
✔ 最佳答案
Let n be the number of bulbs and R be the resistance of each bulb.In a series conection, the total resistance = nR
using Ohm's Law, 10 = 0.01.(nR)
i.e. R = 10/0.01n = 1000/n
In a parallel connection, the equivalent resistance = R/n
using Ohm's Law again, 10 = 1 x (R/n)
i.e. 10 = (1000/n).(1/n)
n^2 = 100
n = 10
Therefore, there are altogether 10 bulbs
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