Final answer:
The QT interval on an ECG represents the time from the start of depolarization to repolarization of the ventricles, including ventricular systole. It is typically around 0.30-0.43 seconds in a normal ECG.
Step-by-step explanation:
The QT interval on an electrocardiogram (ECG) represents the time from the start of depolarization to repolarization of the ventricles, and includes the period of ventricular systole. It is measured from the beginning of the QRS complex to the end of the T wave. In a normal ECG, the QT interval typically ranges from 0.30-0.43 seconds.