worksheet_27.doc

27 Worksheet (A2) 1

A flat coil of  N  turns  turns and cross-sectional area  A is placed in a uniform magnetic field of flux density B. The plane of the coil is normal to the magnetic field. a Write an equation for: i the magnetic flux Φ  th  through the coil [1] ii the magnet magnetic ic flux flux linkag linkagee for for the coil. coil. [1] b The diagram shos the coil hen the magnetic field is at an angle θ to the normal of the plane of the coil. What is the flux linkage for the coil! [1]

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A square coil of N  turns  turns is placed in a uniform magnetic field of magnetic flux density  B. "ach side of the coil has length  x. What is the magnetic flux linkage for this coil!

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The diagram shos a magnet placed close to a flat circular coil. a "xplain hy there is no induced e.m.f. e$en though there is magnetic flux linking the coil. b "xplain hy there is an induced e.m.f. hen the magnet is  pushed toards the coil.

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A coil of cross-sectional area %.& × 1&'% m# and (& turns is placed in a uniform magnetic field. a The plane of the coil is at rightangles to the magnetic field. )alculate the magnetic flux density hen the flux linkage for the coil is 1.% × 1&'% W*  W*. [+] b The coil is placed in a magnetic field of flux density &.,& T. The The normal to the coil is at an angle of & to the magnetic field/ as shon in the diagram. )alculate the flux linkage for the coil. [+]

A0 and A e$el 2hysics

3riginal material 4 )am*ridge 5ni$ersity 2ress #&1&

1

27 Worksheet (A2) 5

A square coil is placed in a uniform magnetic field of flux density densit y %& mT. The plane of the coil is normal to the magnetic field. The coil has #&& turns and the length of each side of the coil is +.& cm. a )alculate: i the magnetic flux Φ  thro  throug ugh h the the coi coill [#] [#] magnetic flux linkage linkage for for the coil. coil. [#] ii the magnetic b The plane of the coil is turned through 6&. What is the change in the magnetic flux linkage for the coil! [#]

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A flat circular coil of 1#&& turns and of mean radius 7.& mm is connected to an ammeter of negligi*le resistance. The coil has a resistance of .+ 8. The plane of the coil is placed at right angles to a magnetic field of flux density &.1, T from a solenoid. The current in the solenoid is sitched off. 9t takes #& ms for the magnetic field to decrease from its maximum $alue to ero. )alculate: a

b

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the a$erage magnitude of the induced e.m.f. across the ends of the coil the a$erage current measured *y the ammeter.

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The diagram shos a straight ire of length 1& cm mo$ed at a constant speed of #.& m s '1 in a uniform magnetic field of flux density &.&,& T.

;or a period of 1 second/ calculate: a the distance tra$elled *y the ire b the area sept * y the ire c the the cha chang ngee in in the the magne agneti ticc flu flux x for for the the ir iree *y the the ir ire? e? d the e.m.f. induced across the ends of the ire using your anser to c the e.m.f. induced across the ends of the ire using  E = Blv. e

[1] [1] [#] [#] [#] [1]

A circular coil of radius 1.# cm has #&&& turns. The coil is placed at right angles to a magnetic field of flux density & mT. )alculate )alculate the a$erage magnitude of the induced e.m.f. across the ends of the coil hen the direction of the magnetic field is  reversed in  in a time of +& ms.

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A0 and A e$el 2hysics

3riginal material 4 )am*ridge 5ni$ersity 2ress #&1&

2

27 Worksheet (A2) 9

The diagram shos a step-up transformer. The ends AB of the  primary coil are connected to a 1., @ cell and a sitch. The sitch is initially closed and the lamp is off. The sitch is suddenly opened and the lamp illuminates for a short time.

"xplain hy the lamp illuminates only for a short period. 0tat 0tatee one one chan change ge to the the app appar arat atus us that that oul ould d all allo o the the lam lamp p to to ill illum umin inat atee nor norm mally ally..

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A ire of length  L is placed in a uniform magnetic field of flux density  B. The ire is mo$ed at a constant $elocity v at right angles to the magnetic field. 5se ;araday>s la of electromagnetic induction to s ho that the induced e.m.f.  E  across  across the ends of the ire is gi$en *y  E = BLv. ence calculate the e.m.f. induced across the ends of a #& cm long rod rolling along a horiontal ta*le at a speed of &.+& m s '1.