## Review Answers

1. Using Ohm's law, V = IR, the derived current is 2 A.

2. The combined resistance in a series circuit is Rcomb = R1 + R2.

3. This is a current divider. The resultant combined resistance is 1/Rcomb = 1/R1 + 1/R2.

4. Capacitive reactance is inversely related to the applied frequency of Ac.

5. In a transformer, the ratio of the coil number defines the step-down or step-up relationships. In this instance, N1/N2 = 20/5 = 4. Therefore, the induced voltage will be 1/4 of the original voltage, or 100 V/4 = 25 V.

6. Impedance is the combined resistances to current flow in a circuit passing AC. It may include not only resistance from a resistor, but also capacitive and inductive reactances.

7. The time constant, t, of a circuit with resistance R and capacitance C is defined by: t = R x C. The time constant, t, refers to the time needed for a capacitor in an RC circuit to reach 63% (1 - 1/e) of its full charge.

8. The voltage reading across the capacitor in an RC circuit behaves as the high-frequency filter. Adjustment of this element may serve to help filter out higher-frequency artifact, such as EMG activity in the recording of an EEG.

9. The Nyquist frequency is the highest input frequency that is deemed desirable to detect. If the Nyquist frequency is 100 Hz, then the sampling frequency should be at least 200 Hz to avoid aliasing.

10. A ground loop occurs when multiple grounds are applied to a subject because of various electrical devices, such as in an intensive care unit setting. If these various grounds are not identical in voltage, an electrical pathway can exist that includes the patient, through which stray currents may travel, thus, endangering the patient. A common ground can avoid this hazard.

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