Current Electricity and Electrical InstrumentHard
Question
A wire of length L and 3 identical cells of negligible internal resistances are connected in series. Due to the current, the temperature of the wire is raised by ᐃT in a time t. A number N of similar cells is now connected in series with a wire of the same material and cross section but of length 2L. The temperature of the wire is raised by the same amount ᐃT in the same time. The value of N is
Options
A.4
B.6
C.8
D.9
Solution
In the first case 
t = ms ᐃT ......(i)
When length of the wire is doubled, resistance and mass both are doubled.
Therefore, in the second case
= (2m)s ᐃT .....(ii)
Dividing Eq. (ii) by (i), we get
2 or N2 = 36 or N = 6.
t = ms ᐃT ......(i)When length of the wire is doubled, resistance and mass both are doubled.
Therefore, in the second case
= (2m)s ᐃT .....(ii) Dividing Eq. (ii) by (i), we get
2 or N2 = 36 or N = 6.Create a free account to view solution
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