Question

A dynamo with an e.m.f. of 120 V and an internal resistance of 0.5Ω and an accumulator battery with an e.m.f. of 110V are connected to an external resistance R as shown in Fig. What is the value of R for which there will be no current flowing through the battery? How will the battery operate when the resistance R is smaller or greater than the above value?

Answer 1

Answer:  R₀ = 5.5 ohms; if R > R₀, the battery will charge; if R < R₀, the battery will discharge.

Explanation:

For no current to flow through the battery, the difference in potential across the terminals of the dynamo must be equal to the e.m.f. of the battery, i.e., V = ε, or, in other words, the potential drop Ir across the dynamo must satisfy the relation