A model to use for enhanced storytelling and the article publishing lectures.
Interest is calculated periodically and added to the savings account. Different types of accounts may calculate interest multiple times a year.
A bank savings account represents a reinforcing structure which produces exponential growth. Considering the interest rates these days the growth probably doesn't seem exponential as it's pretty small.
This is the savings account results
As the current water level gets closer and closer to the desired water level the gap gets smaller and the water flow is reduced. This is a balancing loop because the action is intended to create a balance between the current and desired water levels.
Here's the bathtub filling results.
That wasn't so hard was it!