Sinusoidal current
- 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.
- 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