Four cells each of e.m.f 1.5V and internal resistance of 4\Omega are connected in parallel. What is the effective e.m.f. and internal resistance of the combination?
A
6.0V, 16\Omega
B
6.0V, 1\Omega
C
1.5V, 4\Omega
D
1.5V, 1\Omega
Verified Correct Answer: D.
Step-by-Step Mathematical Solution
Since all the cells are connected in parallel, the effective e.m.f. is just that of one single cell. Which means e.m.f. = 1.5V
However, the effective internal resistance adds as parallel arrangement given as
1/r = 1/r1 + 1/r2 + 1/r3 + 1/r4
= 1/4 + 1/4 + 1/4 + 1/4
= 1\Omega
∴ r = 1\Omega
Answer = 1.5V, 1\Omega
Source: Myschool Past Questions Archive (Record #600)