MODUL SKOR A+ FIZIK JPNS 2014 - ELEKTROMAGNET - SKEMA

8/11/2019 MODUL SKOR A+ FIZIK JPNS 2014 - ELEKTROMAGNET - SKEMA

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SKEMA MODUL ELECTROMAGNETIC (BEST WESTERN)

Soalan 1

1 6(a) 1 State the meaning of induced current correctly

The current that is induced by electromagnetic inductions when the

circuit is complete//The current that can be produced without any

electrical supply/source

2 (b) (i) 2 Label the polarity of each solenoid correctly

1 X: N

2 Y: S

2 (ii) 2 Label the direction of motion of each magnet correctly

Diagram 6.1 bar magnet towards the solenoid

Diagram 6.2 bar magnet away from the solenoid

2 (c) (i) 2 State the type of force correctly

1 Repulsive

2 Attractive

1 (ii) 1 Name the law correctly

Lenzs Law

1 (d) 1 Correct suggestion

Increase the speed of bar magnet/increase the number of turns of

the solenoid/use a stronger magnet

8

Soalan 2

NO.SECTION A

MARKING CRITERIA

MARK

SUB TOTAL

7(a)(i) State the type of transformer correctly

- Step-down transformer

1


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7(a)(ii)

7(b)

7(c)(i)

7(c)(ii)

7(d)

State the reason correctly

- Easy to magnetize//easy to demagnetize//increase the magnetic field

Show a correct substitution

- 12 X 1500 240

Answer

- 75 turns

Shows a correct substitution

- 0.1 X 240 X 0.85//0.1 X 240 X 85/100

Answer with correct unit

- 20.4 W

State the modification correctly

- Laminated soft iron core- Both the primary coil and secondary coil wound on the middle portion.

Give 3 any explanation correctly

1. when the current in primary coil increase

2. The growth of the magnetic field in primary coil cause the magnetic fieldto cut through the secondary coil

3. e.m.f is induced in the secondary coil4. when the current in primary coil decrease

5. the magnetic field collapse in primary coil cause the magnetic field tocut through the secondary coil

1

1

1

1

1

1

1

1

1

1

1

1 10

Soalan 3

8 (a) An electromagnet is a magnet in which a magnetic field is produced by the flow

of electric current.

1

(b) (i) Increase the current.

The strength of an electromagnet increases

1

1

(ii) Soft-Iron core

Easily magnetised and demagnetised

1

1

(iii) Increase the number of turns.

The strength of an electromagnet increases

1

1

(c) L 1


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(d) Increase // More

The poles for a U-shaped electromagnet are closer together

1

1

(e) P= mgh

t

= 250 x 10 x 45

= 2000 W

1

1

Soalan 4

10.(a)

(b)(i)

(ii)(iii)

(iv)

(c)

(d)

The current produced when the magnetic flux is cut across by a conductor//Changing of flux at conductor

10.2 - no relative motion between the magnet and the coil //10.3 - there is relative motionNumber of turns in 10.3 is less than number of turns in 10.4Number of turns increases,The change in magnetic flux increasesInduced current increasesFaradays Law

Magnetic flux is cut , induced current is producedWhen = 90 o maximum current produced // = 0 o minimum current producedCommutator is used to ensure the direction of the current that flows throughthe external circuit is in one direction

Suggestion Rationale

1. Step down transformer To reduce voltage

2. Ns : Np = 240 : 6 = 40 : 1 To reduce 240V to 6V

3. Use diode To change AC to DC

4. Use capacitor To smooth the output current

5. Use laminated soft iron core To reduce heat loss due to eddycurrent

1

1

1

11

11

1

1

10


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Soalan 5

12(a) Defines correctly

- Current that flows in one direction 1 1

(b) State that the magnets produce a magnetic field- The (magnadur) magnets produce a magnetic field / diagram 1

State that the current in the wire produces a magnetic

field

- The current in the wire produces a magnetic field / diagram 1

State that the two fields combine to form a resultant

catapult field

- The two magnetic fields interact/combine to form a

resultant / catapult field/ diagram

1

Diagram showing the catapult field and the force labelled

1 4(c) M1 State a suitable density

- Low density material 1

M2 State the reason for M1 correctly

- Coil has smaller mass / lighter 1

M3 State a suitable number of turns

- High number of turns 1


- Larger force acting on the coil / higher electromagnetic field

strength 1

M5 State a suitable strength of magnet

- High strength magnets 1


- Larger force acting on the coil 1

S N


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M7 State a suitable number of segments- More segments 1


- Coil rotates smoothly 1

M9 Choose the most suitable motor

- Motor R 1

M10 State the reason correctly

- Lowest density, high number of turns, high strength

magnets and commutator splits into the most number of

segments1 10

(d) (i) Correct expression or answer3 x 8 // 24 (J) 1

(ii) Correct expression

5

24(e.c.f.)

1

Answer with correct unit

4.8 W 1

(iii) Correct expression

10012

8.4 //

12

8.4 (e.c.f.)

1

Correct answer

40% // 0.4 1 5

20

Soalan 6

10.

(a) 1 Flemming left hand rule

(b) 1

2

3

4

5

Thereading of ammeter in Diagram 10.2 > in Diagram 10.1

Angle of deflection of copper wire coil in Diagram 10.2 > inDiagram 10.1The strength of magnetic field in Diagram 10.1and Diagram

10.2 is the sameThe bigger the reading of ammeter the bigger the deflection

of copper wire coilThe bigger the magnitude of current, the bigger the force oncurrent carrying conductor


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(c) 12

34

Current flow in copper coil produce magnetic fieldAnd interact with magnetic field of permanent magnet

Produce catapult fieldAnd force on copper coil

(d)

1, 2

3, 4

5, 6

7, 8

9, 10

Tot/Jum : 20

Suggestion / Modification Explanation / Reason

Many number of turns of

coil

Increase the strength of

magnetic field produced

Soft iron core To concentrate the magnetic

field line

Curve magnet To produce radial magnetic

field

Lower stiffness The pointer easy to deflect

Strip mirror under thepointer // Has adjustment

screw

Avoid parallax error // tocorrect the zero error

MODUL SKOR A+ FIZIK JPNS 2014 - ELEKTROMAGNET - SKEMA

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