Three cells each of e.m.f 1.5 V and internal resistance 2.5Ω are connected as shown in the diagram above. Find the net e.m.f and the internal resistance
Attached Figure / Diagram
A
1.5V, 7.50Ω
B
1,5V, 0.83Ω
C
4.5V, 7.50Ω
D
4.5V, 0.83Ω
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Since the cells are connected in parallel the net e.m.f is that of one cell, E.
However the effective internal resistance should be added as parallel resistance.
=> 1/v + 1/25 + 1/25 + 1/25 = 1.2
∴ v = 0.83Ω
∴ Effective e.m.f and internal resistance are respectively = 1.5V and 0.83Ω
Source: Myschool Past Questions Archive (Record #14388)