Electrical and Electronic Principles
Electrical and Electronic Principles
The exam tests DC and AC circuits, Ohm's law, power, impedance, grounding, leakage, filters, batteries, sensors, and measurement. Expect calculations tied to patient safety.
Core rules
- V = IR; P = VI = I²R = V²/R.
- Impedance extends resistance to AC; capacitors and inductors cause phase shift.
- Grounding provides a low-impedance fault path; isolation limits patient current.
- Common-mode rejection improves ECG and EEG signal quality; electrode contact and impedance matter.
- RMS and peak differ: 120 V RMS has about 170 V peak.
Worked example
A 120 V source contacts a patient path of 1,000 Ω. I = 120/1,000 = 0.120 A = 120 mA, well above the threshold for ventricular fibrillation risk. If isolation and grounding reduce the current path to 100 µA, safety improves substantially.
Traps
- Mixing RMS and peak values.
- Ignoring source impedance and meter loading.
- Assuming meters are ideal when measuring low currents.