Whathappens in the real worldwhenwedo this type of experiment? For example, if we try to start a car with the headlights already on, we most likely notice the headlights dim as the battery is asked to supply a large (∼100Aor more) starter current in parallel with the current running to the headlights. If we model the 12 V battery with an ideal 12 V source as in Fig. 5.11a, our observation cannot be explained. Another way of saying this is that our model breaks down when the load draws a large current from the source.