A square loop (side a) is mounted on a vertical shaft and rotated at angular velocity ω (Fig. 7.19). A uniform magnetic field B points to the right. Find theεtfor this alternating current generator.

Short Answer

Expert verified

The induced emf in the square loop is .Ba2ωsinωt

Step by step solution

01

Write the given data from the question.

The uniform magnetic field is B .

The side of the square loop is a .

The angular velocity is ω.

02

Calculate the generated emf in the square loop.

εt=-ddt(BAcosωt)The area of square loop,A=a2 .

The square loop is moving at angle with angular velocity in time

tθωt.

The magnetic flus through the loop is given by,

role="math" localid="1657618600560" ϕ=BAcosθ

Substitute ωtfor θinto above equation.

ϕ=BAcosθ

According to the Faraday’s law, the induced emf in any closed loop is equal to the negative of the rate of change of flux in the circuit.

ε(t)=-dϕdt

Substitute ϕ=BAcosωtfor ϕinto above equation.

εt=-ddt(BAcosωt)

Substitute for into above equation.

role="math" localid="1657619049126" εt=-ddt(BAcosωt)εt=-Ba2-sinωt.ωεt=-Ba2sinωt

Hence the induced emf in the square loop is Ba2ωsinωt.

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Most popular questions from this chapter

A perfectly conducting spherical shell of radius rotates about the z axis with angular velocity ω, in a uniform magnetic field B=B0Z^. Calculate the emf developed between the “north pole” and the equator. Answer:localid="1658295408106" [12B0ωα2].

An infinite wire runs along the z axis; it carries a current I (z) that is a function ofz(but not of t ), and a charge density λ(t) that is a function of t (but not of z ).

(a) By examining the charge flowing into a segment dz in a time dt, show that dλ/dt=-di/dz. If we stipulate that λ(0)=0and I(0)=0, show that λ(t)=kt, I(z)=-kz, where k is a constant.

(b) Assume for a moment that the process is quasistatic, so the fields are given by Eqs. 2.9 and 5.38. Show that these are in fact the exact fields, by confirming that all four of Maxwell's equations are satisfied. (First do it in differential form, for the region s > 0, then in integral form for the appropriate Gaussian cylinder/Amperian loop straddling the axis.)

If a magnetic dipole levitating above an infinite superconducting plane (Pro b. 7 .45) is free to rotate, what orientation will it adopt, and how high above the surface will it float?

Suppose a magnetic monopole qm passes through a resistanceless loop of wire with self-inductance L . What current is induced in the loop?

(a) Show that Maxwell's equations with magnetic charge (Eq. 7.44) are invariant under the duality transformation

E'=Ecosα+cBsinα,cB'=cBcosα-Esinα,cq'e=cqecosα+qmsinα,q'm=qmcosα-cqesinα,

Where c1/ε0μ0and αis an arbitrary rotation angle in “E/B-space.” Charge and current densities transform in the same way as qeand qm. [This means, in particular, that if you know the fields produced by a configuration of electric charge, you can immediately (using α=90°) write down the fields produced by the corresponding arrangement of magnetic charge.]

(b) Show that the force law (Prob. 7.38)

F=qe(E+V×B)+qm(B-1c2V×E)

is also invariant under the duality transformation.

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