The working principle of magnetic

1: Principle of magnetic recording
　　Recording head from the annular gap within the core and wrapped around the core composition on a line graph. Card is a piece by a certain material base and evenly coating the film base made of the above magnetic particles. In the records, magnetic cards magnetic surfaces moving a certain speed, or recording heads with a certain speed movement, respectively, and the gap or magnetic recording heads facial contact. Once the pass on the head of the coil current, the void space is generated with the current proportional to the magnetic field, so magnetic contact with the gap part of the magnetic body was magnetized. If the record signal current change over time, then when on a magnetic card through the gap when the magnetic body (because the magnetic card or the head is moving), then with the current changes being magnetized to varying degrees. After being magnetized card, leave the magnetic gap magnetic layer on the left correspond to current changes in remanence.

　　If the current signal (or magnetic field strength) by the sine law of change, then the magnetic flux remaining on the same change in accordance with the sine rule. When the current is positive when elicited a left to right (from N to S) of the magnetic polarity; When the current is reversed, the reverse magnetic polarity followed suit. Its final results can be seen from N to S on the card and then back to N, a wavelength, it can be seen as connecting with the polarity of the two magnetic bar. This is a way to simplify the results, however, it must be remembered that the remanence Br is based on sinusoidal change. When the signal current is maximum, the vertical magnetic flux density reaches the maximum. Record signals to sinusoidal changes in the form of remanence records, stored on the card.

2: Magnetic Card works
　　Above the residual magnetic flux density Br in the magnetic card magnetic course of their work plays a decisive role. To a certain speed through the magnetic coil with the work of heads, magnetic cards magnetic field lines cutting the external coil, induced electromotive force generated in the coil, which transmit the recorded signal. Of course, also requires the work be recorded in the magnetic signal has a wide frequency response, less distortion and higher output levels.

　　A very thin metal line can be used as a simple playback devices. Metal straight lines and magnetic close, direction perpendicular to the direction of magnetic cards, magnetic cards run-time, the metal straight-line cutting magnetic field lines resulting from induced electromotive force, electromotive force and cutting the size of the magnetic field lines is proportional to. When the card's speed remains the same, the metal linear induction electromotive force and magnetic residual magnetic flux density is proportional to the surface, while the conductor of the inductive electromotive force by the following formula, said:
e = BrWv formula Br - surface residual magnetic induction intensity;
W - the width of the track record of Road;
v - playback speed when the magnetic cards.

　　In the case of Br = 2πf/vφrmcos2πft comprehensive Br, and the relation e get e = 2πfWφrmcos2πft. Of course, with a metal wire for magnetic work equipment, due to the output very small and therefore I was not practical. The head is a high permeability coefficient of soft magnetic material of the core, coil winding wrapped around the top, head in front of a very narrow gap, then head of the magnetic flux to enter the work concerned, can be seen as two the effective parallel reluctance, that the gap reluctance and the reluctance core heads. Because the gap is much larger than the work of the effective magnetoresistive heads iron core reluctance, so the vast majority of magnetic flux on the core input to the head, and with the work of the head coil windings on the cross-linking occurred, which induced electromotive force, in this case Under a single replay of metal lines get free induction formulas are fully applicable to the work of annular magnetic heads, but the proportion of coefficients is different. Set N of the coil turns, m for the head and work related to core size and magnetic coefficients, then the ring winding head arising from the work of the induction electromotive force is: e = 2πfWmNφrmcos2πft

　　Because the magnetic windings in the work of the electromotive force induced by the magnetic flux is proportional to the rate of change, that is, EMF e α By α frequency f. In the record i = Isinwt, vertical remanence density Bx α i (transfer curve of the straight part), so, Bx = K1Isinwt. As By α dbx / dt, e α By, therefore, e = K2Iwcoswt. Where K2 depends on the efficiency of the work of the head, turns, tape materials. These formulas also show that: the output voltage proportional to the records of current; the output voltage proportional to the signal frequency; the output voltage to be 90 °, the corresponding change (this change from sine to cosine above).