A 163 ‑turn circular coil of radius 2.65 cm and negligible resistance is immersed in a uniform magnetic field that is perpendicular to the plane of the coil. The coil is connected to a 10.7 Ω resistor to create a closed circuit. During a time interval of 0.149 s, the magnetic field strength decreases uniformly from 0.481 T to zero. Find the energy, in millijoules, that is dissipated in the resistor during this time interval.

Explanation:

change in flux = no of turns x area of coil x change in magnetic field

= 163 x π 2.65² x 10⁻⁴ x ( .481 - 0 )

= 1728.84 x10⁻⁴  weber

rate of change of flux = change in flux / time

= 1728.84 x10⁻⁴ / .149

= 11603 x10⁻⁴ V .

volt induced = 1.16 V

current in the circuit

= volt induced / resistance

1.16 / 10.7 = .1084 A

energy dissipated = i²Rt where i is current , R is resistance and t is time.

= .1084² x 10.7 x .149

= .018734 J

= 18.73 mJ .

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