On standard EKG paper at 25 mm/s and 10 mm/mV, what do one small box represent horizontally and vertically?
Answer choices
- A0.1 second horizontally and 0.1 mV vertically
- B0.04 second horizontally and 1.0 mV vertically
- C0.04 second horizontally and 0.1 mV vertically
- D0.2 second horizontally and 0.5 mV vertically
About this question
What does one small box represent on standard EKG paper? Rate and interval calculations on the CCMA exam assume you know the grid at 25 mm/s and 10 mm/mV. Mixing time with voltage, or small boxes with large boxes, breaks the 300 method and PR/QRS timing. Read the wording and clinical context closely; those details determine the NHA CCMA competency being tested.
This question asks for horizontal and vertical small-box values. At standard settings, one small box is 0.04 second horizontally and 0.1 mV vertically. Five small boxes make a large box of 0.20 second and 0.5 mV. Lock 0.04 s / 0.1 mV before you estimate heart rate or measure intervals. For ekg small box 0 04 second 0 1 mv, sort the likely distractors into the related terms that they actually describe.
Reveal answer & explanationShow
Correct answer
- A0.1 second horizontally and 0.1 mV vertically
- B0.04 second horizontally and 1.0 mV vertically
- C0.04 second horizontally and 0.1 mV verticallyCorrect
- D0.2 second horizontally and 0.5 mV vertically
Basic rationale
One small box equals 0.04 second horizontally and 0.1 mV vertically.
Option explanations
- A: Incorrect. 0.1 second horizontally and 0.1 mV vertically is not the best choice for this scenario.
- B: Incorrect. 0.04 second horizontally and 1.0 mV vertically is not the best choice for this scenario.
- C: Correct. One small box equals 0.04 second horizontally and 0.1 mV vertically.
- D: Incorrect. 0.2 second horizontally and 0.5 mV vertically is not the best choice for this scenario.
Deep Analysis
Core logic
At standard settings, 1 mm is 0.04 s in time and 0.1 mV in voltage; five small boxes make a large box of 0.20 s and 0.5 mV.
Distractor analysis
A: 0.1 second horizontally and 0.1 mV vertically does not match the tested concept. B: 0.04 second horizontally and 1.0 mV vertically does not match the tested concept. D: 0.2 second horizontally and 0.5 mV vertically does not match the tested concept.
Exam trap
Do not swap 0.04 s with 0.20 s.
Memory tip
Small box: 0.04 s by 0.1 mV.
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