Week 5 Review

Question 1

Which of the following is the correct description of “charge”?

Answer 1

Gain or loss of electrons by an atom

Question 2

According to Ohm’s law, when using a device that has a constant voltage, what will happen to the current amplitude when the skin resistance increases?

Answer 2

the current decreases

Question 3

Which type of current will most likely cause changes in the tissues underlying the electrodes as a result of electrode polarity?

Answer 3

direct current

Question 4

Which of the following is true regarding the strength-duration curve for electrical stimulation?

Answer 4

It depicts the response of a nerve to stimulation for a given pulse amplitude and duration.

Question 5

Which electrochemical effects match the given electrode polarity?

Answer 5

the alkaline reaction under the cathode results in softening of the underlying tissues.

Question 6

According to Ohm’s law, an 80 volt (V) circuit passing through 4 ohms of tissue impedance (resistance) will have how many amps (A) of current?

Ohm’s law:

I = V/R or

I (current in amperes) = Voltage/Resistance

Answer 6

20 A

Question 7

Which of the following statements is true about charge?

Answer 7

Charge is neither created nor destroyed.

Question 8

The force of attraction or repulsion created by an electric field that represents potential energy is known as

Answer 8

voltage

Question 9

Why are human body tissues such as muscles, nerves, and blood good conductors of electric current?

Answer 9

These tissues have a high water content and presence of ions.

Question 10

Which of the following is the correct description of “direct current”?

Answer 10

Unidirectional flow of electrons for at least 1 second

Question 11

If the phase durations of a biphasic pulse are 150 μsec each and the interphase (or intrapulse) interval is 50 μsec, what is the total pulse duration?

Answer 11

350 μsec

Question 12

What can be done clinically to decrease impedance between the electrode and the skin?

Answer 12

Use electrodes with gel or adhesive conductive agents.

Question 13

The unidirectional or bidirectional flow of ions or electrodes that periodically ceases for a small period of time before the next electrical event is known as

Answer 13

Pulsed or pulsatile current

Question 14

Why is the electrochemical effect negligible when using monophasic pulsed currents such as high-volt pulsed current (HVPC)?

Answer 14

Short pulse durations and long interpulse intervals prevent accumulation of charges.

Question 15

The greatest amount of electrothermal heating occurs with which of the following currents?

Answer 15

direct current

Question 16

Why does electric current depolarize nerves more easily than it does skeletal muscles?

Answer 16

The resting membrane potential of nerves is less negative than that of muscles.

Question 17

When stimulating a mixed peripheral nerve, which type of nerve fibers will be recruited first?

Answer 17

type A alpha

Question 18

Which of the following describes the typical characteristics of what is commonly known as “Russian current”?

Answer 18

2,500 Hz alternating current, burst modulated at 50 bursts per second using 10-msec bursts

Question 19

Which of the following best describes interferential current (IFC)?

Answer 19

Superimposition of two symmetrical, asynchronous, sinusoidal alternating currents

Question 20

Low-intensity direct current (LIDC) is most commonly used clinically for which of the following?

Answer 20

Promotion of wound healing by augmenting the current of injury

Question 21

Which of the following will occur in a constant current (CC) device if the resistance to current flow in biological tissues increases?

Answer 21

voltage will increase

Question 22

Which of the following correctly describes “pulse duration”?

Answer 22

total time elapsed from beginning to end of all phases, including interphase interval

Question 23

How often can a typical disposable electrode be reused before it should be discarded?

Answer 23

18 to 20 times on average

Question 24

Which of the following statements is correct regarding electrode placement?

Answer 24

The best electrode placement for a given treatment may require some trial and error.

Question 25

What is the relationship between current density and electrode size?

Answer 25

Current density is inversely proportional to electrode size.

Question 26

What will happen to the current density under each electrode if lead wires are bifurcated and attached to multiple electrodes?

Answer 26

Decreased at each individual electrode

Question 27

When using balanced biphasic pulsed current for treatment, what is the correct attachment of the lead wires to the electrodes?

Answer 27

Wire color does not matter for this type of current.

Question 28

Which of the following is NOT believed to occur during treatments using iontophoresis?

Answer 28

electrosaturation
(electroosmosis, electroporation, electromigration)

Question 29

Which of the following is the correct equation for determining the dosage for iontophoresis treatments?

Answer 29

Dosage (mA·min) = Current (mA) × Duration (min)

Question 30

You are using an iontophoresis patch to treat your patient’s lateral epicondylitis with dexamethasone. Using your knowledge of iontophoresis and electrotherapy, you determine the following:

Answer 30

Dexamethasone should be applied to the negative side of the patch.