emi 04-09 collected for revision practice ms

7/27/2019 EMI 04-09 Collected for Revision Practice MS

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7 M09/4/PHYSI/HP2/ENG/TZ1/XX/M+

A4. (a) (i)0

I

;

rmsAI ; [2]

or

rmsVV

;

rms

rmsA

VI

R

;

(ii) 200 W; [1]

(iii) VV ;

2

140 10 WVPR

; [2]

(b)

peak voltage of 200 V; (allow 180 to 200V)

period = 0.50 ms; [2]


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9 N07/4/PHYSI/HP2/ENG/TZ0/XX/M+

B3. Part 1 Magnetic and electrical force fields

(a) (i) use of 212

qV mv ;

19 27 21

2

1.6 10 420 1.67 10 v

5 12.8 10 m sv ; [2]

(ii) arc of circle / continuous curve within region ABCD and deflected upwards

i.e. towards AB;

straight-line as tangent to arc beyond BC; [2]

(iii) 2 19 51.5 10 1.6 10 2.8 10F ;166.7 10 N ; (allow 166.8 10 N ) [2]

(b) (i) arrow pointing down the page; [1]

(ii) 16 196.7 10 1.6 10 E ;3 14.2 10 V mE ; (allow 3 14.3 10 V m ) [2]

(c) (i) induced e.m.f. / current acts in such a direction;

to tend/produce effects to oppose the change causing it; [2]

(ii) e.m.f. constitutes electrical energy;

this energy is derived from working against the change causing the e.m.f.; [2]

Award[1 max]for references to forces against the direction of motion if a

suitable example has been chosen.

(d) (i) change in flux (linkage) 618 10 0.32 0.95 ;6( 5.5 10 Wb)

idea of induced e.m.fN

t

;

6(5.5 10 )

0.34

16 V ; [3]

(ii) side PQ cuts flux but side RS does not cut flux / not move;

so, e.m.f. across QR/PS; [2]

(iii) (as window opens) flux through window would not change;

hence no e.m.f. induced; [2]


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(e) (i) sources whose phase difference is constant; [1]

(ii) the waves from the transmitters interfere;

the path difference varies as the satellite moves and so the amplitude of the

detected (superposed) signal varies as well; [2]Accept references to path difference changing form being an integral or

half integral multiple of the wavelength as the satellite moves.

(iii) three fringe separations in 7.7km ;

hence km57.23

7.7s ;

using km3422.1

16057.2D

s

Ds = 340 km (2 s.d.); [3]

Part 2 Electromagnetic induction

(a) the induced e.m.f. (in a loop) is proportional to the rate of change

of the magnetic flux linkage (in the loop); [1]

(b) (i) as the loop is moved away the magnetic field through the loop is getting

smaller;

hence the magnetic flux through it is changing with time;

Accept also answers based on considerations of induced e.m.f. in eachsection of loop e.g.

e.m.f. is induced in upper and lower section of loop;

no e.m.f. induced in sides/e.m.f. of same sign;

e.m.f. in upper section larger hence current in loop; [2 max]

(ii) the direction of the current is clockwise;

because in this way the magnetic field created by the induced current is in

the same direction as the external magnetic field thus opposing the change

in flux; [2]

Accept any other reasonable formulation based on Lenzs law but not bald

answer without explanation or incorrect explanation.

(iii) work is being performed on the loop by the agent pushing the loop;

against the attractive magnetic force between the loop and the wire;so that the loop moves at constant speed; [3]


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B2.

(a) (i) showing connection via brushes, [1]

(ii) two correct forces; [1]

(iii) when the split ring is in contact with the brushes the current in the coil will

always be in the same direction / OWTTE;some statement to the effect that this will be so even after the coil has

rotated through 180D and sides of coil are reversed;

when the split ring is not in contact with the brushes, the momentum of the

coil will keep it rotating / OWTTE; [3]

(b) (i) tension in thread

weight of object

tension in thread;

weight (of object) / mg;

tension length > weight length; [3]

(ii)2

2sa

t= ;

2

2

2 0.840.35ms

(2.2)

= = ;

T mg ma =

;( ) 0.015 10.35 0.16 NT m g a= + = = ; [4]


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(c) (i) measure the time it takes the object to go successive distances of say 10 cm / any

realistic length given or implied;

if the times are equal then speed is constant / OWTTE; [2]

(ii) increase in potential energy 0.015 10 0.84 0.13J= = ;

rate of working =power input0.13

0.037 W3.4

= = ; [2]

(iii) power input to motor 6.0 0.045 0.27 WVI= = = ;

0.0370.14

0.27

out

in

PEff

P= = = or14%; [2]

(d) lg( )E against lg( )I ;

lg( ) lg( ) lg( )E k n I= + ;

slope/gradient n= ; [3]

(e) (i) a magnetic flux links the coil;

as the coil rotates the flux linkage changes with time;

therefore, from Faradays law an e.m.f. will be induced; [3]

(ii) the faster the speed of rotation, the greater the flux change;

Faradays law states that the e.m.f. is equal/proportional to the rate of change of

flux; [2]

(iii) the amount of flux linking the coil changes with the angle that the coilmakes with the magnetic field / OWTTE; [1]

(f) (i) any maximum/minimum value ofV; [1]

(ii) from the graph0

2.0VV = ;

therefore, 0rms

1.4V2

VV = = ; [2]


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(d) (i) (induced) e.m.f. proportional to rate of change of magnetic flux (linkage); (do not

allow induced current)

as current increases, magnetic field in coil increases;

thus change in flux linkage and e.m.f. induced; [3]

(ii) direction of (induced) e.m.f. such as to tend to oppose;

the change producing it;

induced e.m.f. must oppose e.m.f. of battery / growth of current in circuit; [3]

(iii) energy is supplied by the battery;

in making charge move against the induced e.m.f.; [2]

7 M04/431/H(2)M+


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A4. (a) (i) out of the paper ; [1]

(ii) to the left ; [1]

For (i) and (ii) award[1 max]if labels are missing.

(b) (i) E Blv 0.2 0.3 5.5 0.33 V; [1]= = % % =

(ii) F BIL 0.2 0.8 0.30 0.048 N; [1]= = % % =

(c) P Fv 0.048 5.5 0.26 W;= = % =

EI 0.33 0.80 0.26 W; [2]= = % =

6 M04/432/H(2)M+

emi 04-09 collected for revision practice ms

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