Final answer:
The first positive deflection following the P wave on an ECG is the R wave, which is part of the QRS complex and is always positive.
Step-by-step explanation:
The first positive, or upward, deflection following the P wave on an electrocardiogram (ECG) is known as the R wave, and it is part of the QRS complex. Therefore, the first positive deflection after the P wave is always positive. This segment corresponds to ventricular depolarization, which is necessary for ventricular contraction. The ECG's characteristic pattern aids in diagnosing various cardiac conditions and monitoring heart health.