ECG Electrocardiogram Knowledge Answers and Questions 2 — Questions and Answers
Question 1: Which lead is considered the ground (reference) electrode in a standard 12-lead ECG?
- Right leg (RL) (Correct answer)
- Left leg (LL)
- Right arm (RA)
- V6
Correct answer: Right leg (RL)
The right leg electrode serves as the ground and does not contribute to any waveform.
Question 2: At standard calibration, one small (1 mm) box on the horizontal axis represents how much time?
- 0.04 seconds (Correct answer)
- 0.20 seconds
- 0.10 seconds
- 1.0 second
Correct answer: 0.04 seconds
Each small box equals 0.04 seconds when paper runs at 25 mm/sec.
Question 3: The P wave on an ECG represents which electrical event?
- Atrial depolarization (Correct answer)
- Ventricular depolarization
- Ventricular repolarization
- Atrial repolarization
Correct answer: Atrial depolarization
The P wave reflects depolarization spreading across the atria.
Question 4: Where should the V1 chest electrode be placed?
- 4th intercostal space, right sternal border (Correct answer)
- 4th intercostal space, left sternal border
- 5th intercostal space, midclavicular line
- 5th intercostal space, anterior axillary line
Correct answer: 4th intercostal space, right sternal border
V1 is positioned in the 4th intercostal space just right of the sternum.
Question 5: A standard ECG is normally calibrated so that 10 mm of vertical deflection equals what voltage?
- 1 millivolt (Correct answer)
- 0.5 millivolt
- 2 millivolts
- 10 millivolts
Correct answer: 1 millivolt
Standard calibration sets 10 mm vertical equal to 1 mV.
Question 6: Which artifact is most likely caused by patient muscle tremor or shivering?
- Somatic (muscle) tremor artifact (Correct answer)
- Wandering baseline
- 60-cycle interference
- Flat line
Correct answer: Somatic (muscle) tremor artifact
Muscle movement produces irregular, jagged somatic tremor artifact.
Question 7: The normal duration of a QRS complex in an adult is approximately:
- 0.06 to 0.10 seconds (Correct answer)
- 0.12 to 0.20 seconds
- 0.20 to 0.40 seconds
- 0.40 to 0.60 seconds
Correct answer: 0.06 to 0.10 seconds
A normal QRS complex lasts less than 0.12 seconds, typically 0.06 to 0.10.
ECG Electrocardiogram Knowledge Answers and Questions 2
Which lead is considered the ground (reference) electrode in a standard 12-lead ECG?