MadSci Network: Engineering

Re: How does an analog magnetic tape recording head work? Precisely!

Date: Fri Oct 23 01:37:54 1998
Posted By: Gus Calabrese aka puppet boy, Design Engineer
Area of science: Engineering
ID: 908852210.Eg

Well, here is my first shot at it.  You can submit further questions to me 
so that I know where you want to go.

1)  If magnetic lines of force move at a right angle with respect to a 
wire, current flows through the wire.  One way to create these moving lines 
is to move a wire past a magnet.  Another way is to move the magnet past 
the wire.  There are two ways to increase the current: a) Increase the rate 
at which the magnet and wire move with respect to each other b) Increase 
the magnitude of the magnetic field.

2)  If a current is passed through a wire, a magnetic field forms around 
the wire.  The strength of the magnetic field is related to the amount of 
current passing through the wire.

3)  Magnetic recording tape contains particles that can be magnetized by a 
nearby magnetic field which aligns the magnetic domains in each particle.  
Once the field is removed, the particle remains magnetized.

4)  Moving tape in front of a read head causes the magnetized particles to 
move field lines across the wires which are contained in the read head.  
Generally, the faster the tape moves with respect to the head, the more 
signal level which is developed.  At the same time, higher frequency 
signals can be reproduced.

5)  A record head has a varying current passed through it. At the same time 
the tape is moving past the head.  The particles are magnetized to a 
magnitude and in a direction consistent with the strength of the current 
and the direction of the current respectively.

Let me know what else you would like to know regarding tape recording.

Gus Calabrese

In a video tape recorder, the head which contains a coil is moved 

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