Phy Test3 Ms

KING’S COLLEGE – SECONDARY 5C Tests – Marking Schemes

Ref.: phy_test3_ms.doc

Subject:

Physics

Syllabus:

Chapter 17

Max marks:

40

Part 1

Multiple-choice Questions (20 marks)

1

2

3

4

5

6

7

8

9

10

B

C

D

D

C

A

B

B

B

D

11

12

13

14

15

16

17

18

19

20

A

A

C

B

C

B

C

D

C

D

Part 2

Long Questions (20 marks)

1.

Solutions

Marks

(a)

A downward force acts on side AB. An upward force acts on the side CD. No force acts on the sides BC and AD.

1A 1A 1A 1A

(b)

Since the forces act on the sides as in (a), the coil rotates in anti-clockwise direction as viewed by the observer at first. Then the coil passes the vertical plane (at 1/4 turn) owing to its inertia. Since the directions of the forces acting on the sides AB and CD do not change, After passing the vertical plane, the coil changes its rotation direction and passes the vertical plane again. The coil then vibrates about the vertical plane several times and comes to rest. (For effective communication)

2. (a)

1A 1A 1A 1A 1A 1C

Solutions

Marks

When current flows in the coil from A, the cone moves to the right.

1A

N F B-field S B-field F N

(Correct direction of magnetic field.) (Correct direction of the current.) (Correct direction of the electromagnetic force.)

Secondary 5/Tests – Marking Schemes/phy_test3_ms.doc

1A 1A 1A

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KING’S COLLEGE – SECONDARY 5C Tests – Marking Schemes

Ref.: phy_test3_ms.doc

(b)

Since current from the a.c. supply flows backwards and forwards along the coil, by Fleming's left-hand rule, the cone moves backwards and forwards. This stretches and compresses the air in front of the loudspeaker and forms sound.

1A 1A 1A

(c)

(i) (ii) (iii)

1A 1A 1A

The loudness of the sound produced decreases. The pitch of the sound produced increases. The loudness of the sound produced increases.

Secondary 5/Tests – Marking Schemes/phy_test3_ms.doc

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