Question

An energy source will supply a constant current into the load if its internal resistance is?

• A. equal to the resistance of the load
• B. very large as compared to the load resistance
• C. zero
• D. Non-zero but less than the resistance of the load

Answer 1

The correct option is B

very large as compared to the load resistance

1. We know that the current through the load resistance is given by $I=\frac{E}{(R+r)}$, where $E$ is the e.m.f of the cell, $R$ is the load resistance, and $r$ is the internal resistance.
2. As, $r$ and $E$ are constant values, and $R$ is a variable, for the current $I$ to be constant, it should be independent of $R$.
3. When the value of $r$ is very large when compared to that of $R$, then $R+r=r$
4. Thus, $I\approx \frac{E}{r}$, where the value of $I$ also remains constant.

Hence, the correct answer is (B) very large as compared to the load resistance.