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  4. The potential across a generator is 125V when it is delivering 10A. When it delivers 30A the potential is 120V. What are the resistance of armature and induced e.m.f. ?

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Q. The potential across a generator is 125V when it is delivering 10A. When it delivers 30A the potential is 120V. What are the resistance of armature and induced e.m.f. ?

Electromagnetic Induction

Solution:

Using V = E - $ir$ , we get, 125 = E - 10r ....$(i)$
and 120 = E - 30r ...$(ii)$
Subtracting $(ii)$ from $(i)$, 5 = 20$r$ or $r$ = 0.25$\Omega$
from $(i)$ 125 = E - (10 $\times$ 0.25)
or E = 125 + 2.5 = 127.5 V