Lead II records electrical activity between which two electrodes?

• A. RA to LA
• B. Right arm to left leg
• C. Left arm to left leg
• D. Right leg to left arm

Answer: (B)

Lead II is one of the standard limb leads and is defined by measuring the electrical potential difference along the line from the right arm to the left leg. The activity is recorded with the right-arm electrode as the negative input and the left-leg electrode as the positive input, so the lead essentially tracks electrical activity moving from the right shoulder toward the left leg. This diagonal path often aligns well with the heart’s overall electrical axis, which is why Lead II is commonly prominent in ECG tracings.

The other pairs correspond to different leads: the left arm to right arm defines another limb lead, left arm to left leg is a separate lead, and the right leg is typically used as a grounding reference rather than as a recording electrode for these limb leads.