Electricity from Magnetism 1. Computers store memory by spinning a stack of magnetic-coated plates beneath an electromag

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Electricity from Magnetism
1. Computers store memory by spinning a stack of magnetic-coated
plates beneath an electromagnetic head. Suppose a head consisting
of a 148-turn coil wrapped around an iron ring with an area of 1.25
× 10-8 m2. The head is parallel to a magnetic field that changes by
5.2 × 10-4 T in 8.5 × 10-9 s. What is the induced emf in the
coil?
2. A coil with 205 turns of wire, a total resistance of 23 Ω,
and a cross-sectional area of 0.25 m2 is positioned with its plane
perpendicular to the field of a powerful electromagnet. What
average current is induced in the coil during the 0.25 s that the
magnetic field drops from 1.6 T to 0.0 T?
3. An electromagnet that has a mass of almost 8.0 × 106 kg was
built at the CERN particle physics research facility in
Switzerland. As part of the detector in one of the world’s largest
particle accelerators, this magnet creates a fairly large magnetic
field with a magnitude of 0.50 T. Consider a coil of wire that has
880 equal turns. Suppose this loop is placed perpendicular to the
magnetic field, which is gradually decreased to zero in 12 s. If an
emf of 147 V is induced, what is the area of the coil?
4. A 505-turn circular-loop coil with a diameter of 15.5 cm is
initially aligned so that its plane is perpendicular to Earth’s
magnetic field. In 2.77 ms, the coil is rotated 90.0° so that its
plane is parallel to Earth’s magnetic field. If an average emf of
0.166 V is induced in the coil, what is the value of Earth’s
magnetic field?