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A metal detector uses a changing magnetic field to detect metallic objects. Suppose a metal detector that generates a uniform magnetic field perpendicular to its surface is held stationary at an angle of 15.0∘ to the ground, while just below the surface there lies a silver bracelet consisting of 6 circular loops of radius 5.00 cm with the plane of the loops parallel to the ground. If the magnetic field increases at a constant rate of 0.0250 T/s, what is the induced emf E? Take the magnetic flux through an area to be positive when B⃗ crosses the area from top to bottom.

Respuesta :

Answer:

[tex]-1.14 \cdot 10^{-3} V[/tex]

Explanation:

The induced emf in the loop is given by Faraday's Newmann Lenz law:

[tex]\epsilon = - \frac{d \Phi}{dt}[/tex] (1)

where

[tex]d\Phi[/tex] is the variation of magnetic flux

[tex]dt[/tex] is the variation of time

The magnetic flux through the coil is given by

[tex]\Phi = NBA cos \theta[/tex] (2)

where

N = 6 is the number of loops

A is the area of each loop

B is the magnetic field strength

[tex]\theta =15^{\circ}[/tex] is the angle between the direction of the magnetic field and the normal to the area of the coil

Since the radius of each loop is r = 5.00 cm = 0.05 m, the area is

[tex]A=\pi r^2 = \pi (0.05 m)^2=0.0079 m^2[/tex]

Substituting (2) into (1), we find

[tex]\epsilon = - \frac{d (NBA cos \theta)}{dt}= -(NAcos \theta) \frac{dB}{dt}[/tex]

where

[tex]\frac{dB}{dt}=0.0250 T/s[/tex] is the rate of variation of the magnetic field

Substituting numbers into the last formula, we find

[tex]\epsilon = -(6)(0.0079 m^2)(cos 15^{\circ})(0.0250 T/s)=-1.14 \cdot 10^{-3} V[/tex]

Answer:

Induced emf, [tex]\epsilon=-1.13\times 10^{-3}\ volts[/tex]

Explanation:

It is given that,

Number of circular loop, N = 6

A uniform magnetic field perpendicular to its surface is held stationary at an angle of 15 degrees to the ground.

Radius of the loop, r = 5 cm = 0.05 m

Change in magnetic field, [tex]\dfrac{dB}{dt}=0.025\ T/s[/tex]

Due to the change in magnetic field, an emf will be induced. Let E is the induced emf in the coil. it is given by :

[tex]\epsilon=\dfrac{d\phi}{dt}[/tex]

[tex]\phi[/tex] = magnetic flux

[tex]\epsilon=\dfrac{d(NBA\ cos\theta)}{dt}[/tex]

[tex]\epsilon=-NA\dfrac{d(B)}{dt}[/tex]

[tex]\epsilon=6\times \pi (0.05)^2\times 0.025\times cos(15)[/tex]

[tex]\epsilon=-1.13\times 10^{-3}\ volts[/tex]

So, the induced emf in the loop is [tex]1.13\times 10^{-3}\ volts[/tex] . Hence, this is the required solution.

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