2. SINUSOIDAL CURRENT
DEFINITION :
Sinusoidal currents are evenly alternating sine wave
currents of 50 Hz.
This gives 100 pulses in each second of 10ms each , 50 in
one direction and 50 in an other.
3. Cont….
It is produced from the mains by reducing
the voltage to 60 to 80v the step down
transformer.
4.
5. A sinusoidal voltage and current values
FREQUENCY (f) : The number of cycles per second
,It is measured in hertz (Hz)
f = 1 / T
PERIOD (T) : The time taken for the signal to
complete one cycle
It is measured in seconds (s)
T = 1 / f
6.
PEAK VALUE or AMPLITUDE : The maximum value
of
a waveform .
7. INSTANTANEOUS VALUE : The value of voltage
at one particular instant (any point)
EFFECTIVE VALUE : The value of alternating
voltage that will have the same effect on a
resistance as a comparable value of direct
voltage will have on the same resistance .
8. General physiologic effects
When an electric current is passed through the body a
change of concentration of ions occurs at the cell
membranes .
If it occurs at the nerve membrane : contraction
If it occurs in other tissues : ionic movement of tissue
fluid and other constituents .
9. USES
It is usually surged to
cause rhythmical muscle contractions.
It relieves pain and reduces edema.
Because of marked sensory stimulation this current is
often applied to large areas and rarely used for local
muscle stimulation.
10. Indication and contraindication
oIndications
• Pain
• Pain and swelling: 10 minutes unsurged + surged=
alternation of the semi permeability of the cell
membrane , allowing the diffusion of ions and
absorption of exudate.
11. Contraindication
Skin lesions – acne ,dermatitis
,eczema,
Infections – may be aggravated
and possibly spread.
Impaired sensation
