EXAMPLE 21.3 Induced emf in a coil of wire In this example we\'ll see how an emf

Question

EXAMPLE 21.3 Induced emf in a coil of wire In this example we'll see how an emf can be induced by a changing magnetic field. A circular coil of wire with 500 turns and an average radius of 4.00 cm is placed at a 60 angle to the uniform magnetic field be tween the poles of a large electromagnet. The field changes at a rate of -0.200 T/s What is the magnitude of the resulting induced emf? Video Tutor Solution SOLUTION B 400 cm SET UP Figure 21.9 shows our sketch. We remember that is the angle between the magnetic field and the normal to the coil and thus is 30, not 60. The area of the coil is A (0.0400 m) 0.00503 m2 730 SOLVE To find the magnitude of the emf, we use Equation 21.4 :-N ,a/ar/. we first need to find the rate of change of the magnetic FIGURE 21.9 Our sketch for this problem

Explanation / Answer

practice problem

induced emf is e = N*(dphi_B)/dt *cos(phi)

e = N*(dB/dt)*A*cos(phi)

given that

N = 300

dB/dt = 0.25 T/s

A = pi*r^2 = 3.142*(0.03^2) = 2.83*10^-3 m^2

phi = 40 deg

e = 300*0.25*2.83*10^-3*cos(40)

e = 0.162 V

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