What is the current induced in the coil?

+3 votes

A strong electromagnet produces a uniform magnetic field of 1.60 T over a cross-sectional area of 0.330 m2. A coil having160 turns and a total resistance of 21.0 Ω is placed around the electromagnet. The current in the electromagnet is then smoothly reduced until it reaches zero in 20.0 ms. What is the current induced in the coil?
 A

asked Feb 28, 2012 in Physics by apush ~Expert~ (552 points)
    

1 Answer

+1 vote

To find the current we need to first determine Emf, (voltage), and then use Ohm's law to calculate current

Emf =  - dΦB/dt = - d/dt (B*A*N)


B = 1.6 T

A = 0.33 m^2

N = 160 turns

R = 21 Ω

d/dt = 1/ 20 ms = 1/(20*10^-3) s

Solving for Emf we get:(*note negative is removed since we don't care about direction)

Emf = (1/(20*10^-3) s) (1.6 T*(0.33 m^2)*160)

Emf = 4224 V

Using Ohm's Law, 

Current = Voltage / Resistance 

Hence:

Current = 4224 V/ 21Ω  = 201 A

 

answered Mar 8, 2012 by pokemonmaster ~Expert~ (3,856 points)

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