Magnetic information on hard drives is accessed by a read head that must move ra
ID: 1318450 • Letter: M
Question
Magnetic information on hard drives is accessed by a read head that must move rapidly back and forth across the disk. The force to move the head is generally created with a voice coil actuator, a flat coil of fine wire that moves between the poles of a strong magnet, as in the figure. Assume that the coil is a square 1.0 cm on a side made of 230 turns of fine wire with total resistance 1.7? . The field between the poles of the magnet is 0.29T ; assume that the field does not extend beyond the edge of the magnet. The coil and the mount that it rides on have a total mass of 15g
Part A) If a voltage of 5.0 V is applied to the coil, what is the current?
Part B) If the current is clockwise viewed from above, what is the direction of the net force on the coil?
Part C) What is the magnitude of the net force on the coil?
Part D) What is the magnitude of the acceleration of the coil?
a. Directed up in the "Top view" figure. b. Directed down in the "Top view" figure. c. Directed to the left in the "Top view" figure. d. Directed to the right in the "Top view" figure.Explanation / Answer
Given that the magnitude of magnetic field is B = 0.29 T
Number of turns in the coil is N = 230
Resistance of wire is R = 1.7 ?
Length of the square is L = 1.0 cm = 0.01 m
Total mass of coil is m = 15 g = 0.015 kg
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a)
The current in the coil is I = 5.0V / R
= 2.94 A
b)
c)
Magnetic force on the coil is F = NBIL sin?
= 230*0.29T*2.94A*0.01m*sin90o
= 1.961 N
d)
The acceleration of the coil is a = F /m
= 1.961 N / 0.015 kg
=130.73 m/s2
b. Directed down in the "Top view" figure.Related Questions
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