Monday, November 15, 2010

SPM Trial MARA 2010 ~ paper 2 ( CRO )

Question 4

A cathode ray oscilloscope ( C. R. O) is an instrument that converts electronic and electric signals to a visual display.

Diagram 4.1 shows the structure of a simple cathode ray oscilloscope (CRO).
Rajah 4.1 menunjukkan struktur satu osiloskop sinar katod ringkas (OSK) .


(a) (i) Based on Diagram 4.1, name the component T.
Berdasarkan Rajah 4.1, namakan komponen T.

Hints for solving the problem (ii) and (iii) :
The process of emission of electrons from the surface of a heated metal is known as thermionic emission.


This is because some of the electrons have gained enough kinetic energy to break free from the metal surface and escape to the surroundings.

(ii) Explain what happens to the electrons on the surface of T when T is heated.

Terangkan apa yang berlaku kepada elektron pada permukaan T jika T dipanaskan.

(iii) Name the physics process in (a)(ii).
Namakan proses fizik yang berlaku dalam (a)(ii).

(b) A student uses a CRO to study the output voltage of a bicycle dynamo. The time-base is set at 100 ms/division and the Y gain control is set at 0.5 V/division.

Seorang pelajar menggunakan OSK untuk mengkaji voltan output yang dijana oleh sebuah dinamo basikal. Dasar masa telah dilaraskan pada 100 ms/bahagian dan gandaan Y dilaraskan pada 0.5 V /bahagian.


Hits for solving the problem:



(i) Calculate the frequency of the wave produced by the bicycle dynamo.
Hitungkan frekuensi gelombang yang dihasilkan oleh dinamo basikal.

Hits for solving the problem:
f = 1/ T

(ii) On Diagram 4.2, draw a new trace to show the voltage output if the frequency of the dynamo is doubled.

Pada Rajah 4.2, lukiskan surihan yang baru untuk menunjukkan voltan output jika frekuensi dinamo digandakan.



Suggested answers:

a)

(i) Cathode

(ii)Cathode or T emits electrons when it is heated.

(iii) Thermionic emission

b)

(i) time taken to complete one oscillation , T = 4 x 100 ms

T= 400 ms

Frequency , f = 1 / T

f = 1/ 400 ms

f = 2.5 Hz

(ii)




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