Trial Physics 2012

7/29/2019 Trial Physics 2012

1/11

Diagram 7

7. Diagram 7 shows a transistor circuit functioning as an automatic switch. The

resistance of the light dependent resistor (LDR) varies from 2 k to 10 k with

changes in light intensity. The lamp will be switched on when the potential difference

across YZ is more than 4 V.

Rajah 7 menunjukkan sebuah litar yang berfungsi sebagai suis automatic. Rintangan

bagi perintang peka cahaya (PPC) berubah dari 2 k ke 10 k dengan perubahan

dalam keamatan cahaya. Lampu akan dipasang apabila beza keupayaan merentasi

YZ adalah lebih daripada 4 V.

(a) What is the function of resistor R?

.

[1 mark]/[1 markah]

(b) i) Calculate the potential difference across YZ when it is completely

dark.

Hitung beza keupayaan merentasi YZ apabila gelap sepenuhnya.

[2 marks]/[2 markah]

ii) Will the lamp be switched on? Explain your answer.

Adakah lampu akan terpasang? Jelaskan jawapan anda.


10 k

60W, 240 V

X

Y

ZLamp

Lampu

240

LDR

PPC


2/11

(c) Explain why the lamp is connected to a magnetic relay M.

Terangkan mengapa lampu itu disambungkan kepada geganti magnet M.

[2 marks]/ [2 markah]

(d) The circuit in Diagram 7 can be modified to be a heat-controlled automatic switch. By

adding a thermistor and an alarm, explain the modification to the circuit so that the

alarm will be switched on when there is a fire.

Litar dalam Rajah 7 boleh diubahsuai untuk menjadi suis kawalan haba automatic.

Dengan menambahkan satu thermistor dan penggera, jelaskan pengubahsuaian

kepada litar itu supaya penggera akan terpasang apabila kebakaran berlaku.

..

..

.



3/11

Diagram 8/Jadual 8

8. Diagram 8 shows a quality control system where fruit juice carton with volume less

than the minimum requirement will be picked out.Rajah 8 menunjukkan suatu system kawalan kualiti dimana kotak jus minuman

dengan isipadu yang kurang daripada keperluan minimum akan diasingkan.

Table 8 shows four radioisotopes with their respective properties.

Jadual 8 menunjukkan empat radioisotope dengan ciri-ciri masing-masingnya.

Radioisotopes

Radioisotop

Physical states

Keadaan fizikal

Types of radiation

Jenis sinaran

Half-Life

Separuh hayat

Sodium-24

Natrium-24

Liquid

Cecair

Gamma

Gama

15 hours

15 jam

Phophorus-32

Fosforus-32

Liquid

Cecair

Beta

Beta

14.3 days

14.3 hariCobolt-60

Kobolt-60

Solid

Pepejal

Gamma

Gama

5.27 years

5.27 tahun

Strontium-90

Strontium-90

Solid

Pepejal

Beta

Beta

28.5 years

28.5 tahun

Table 8

(a) What is meant by radioisotope?

Apakah maksud radioisotope?

.

[1 mark]/[1 markah]

(b) Based on table 8 state the suitable properties of the radioisotope to detect the

volume of fruit juice . Give one reason for the suitability of the properties.

Berdasarkan jadual 8 di atas, nyatakn ciri-ciri yang sesuai bagi radioisotop

mengesan isipadu jus buah-buahan. Berikan satu sebab bagi kesesuaian ciri-ciri tersebut.

i) Physical state and reason

Keadaan fizikal dan sebab


Fruit juice carton

Kotak jus buah-buahanRadioactive source

Sumber radioaktifRadiation detector

Pengesan sinar


4/11

ii) Type of radiation and reason

Jenis sinaran dan sebab

[2 marks]/[2markah]

iii) Half-life and reason

Separuh hayat dan sebab

..


(c) Based on the answer in 8(b), determine the most suitable radioisotope in Table

8 to detect the volume of fruit juice.

Berdasarkan jawapan dalam 8(b), tentukan radioisotop dalam Jadual 8 yangpaling sesuai untuk mengesan isipadu jus buah-buahan.

[1 mark]/[1 markah]

(d) What will happen to fruit juice carton if the volume of juice inside very low?

Explain your answer.

Apakah yang akan berlaku kepada kotak jus minuman yang mengandungi

isipadu yang sangat sedikit.

.

.


(e) The half-life of sodium-24 is 15 hours. Calculate the time taken for the activity

of sodium-24 to reduce to 12.5% of its initial value.

Separuh hayat bagi natrium-24 adalah 15 jam. Hitungkan masa yang

diambil untuk aktiviti natrium-24 berkurangan menjadi 12.5% daripada nilai

asalnya.


.


5/11

MARKING SCHEME

No Answer Marks/

7 a To limit the current entering the base of the transistor 1

b i. V BC = 10 k x 12

10 k + 10 k= 6 V

ii. Yes

Because V XY = 6V 4 V

1

1

1

1

c 1. The voltage of transistor of 12V is not able to light up the

lamp which requires a voltage of 240 V

2. A magnetic relay is used to switch on the lamp in a 240 V

circuit.

1

1

d 1. The 10 k resistor is replaced with a thermistor.

2. The LDR is replaced with 10 k resistor3. The lamp is replaced with a fire alarm

1

11

Total 10 marks

8 a Isotope which decays by emitting radioactive rays 1

b i. solid

easy to manage and carry

ii. Beta ray

able penetrate the fruit juice carton and less dangerous

iii. Long half-life

More lasting

1

1

1

1

1

1

c Strontium-90 (solid, beta ray and has long half life) 1

d Will be removeIts volume is less than the standard volume.

11

e Time = (3)(5)

= 15 hours

1

1

Total 12 marks


6/11

7. Diagram 7.1 shows silicon atoms, each with four valence electrons in its

outer most shell.

Rajah 7.1 menunjukkan atam silicon, dimana setiap satunya mempunyai empat

elektron yang bebas.

(a) (i) What is meant by doping?Apakah maksud doping?

...

[1 mark]

(ii) Name the majority charge carrier in the p-type semiconductor.

Namakan pembawa cas majoriti di dalam semikonduktor jenis p.

...

[1 mark]

(b) Diagram 7.2 shows a circuit containing a transistor used to detect the

temperature of a liquid. The light bulb L will glow when the base-emitterpotential difference VBE is more than 3 V.

Rajah 7.2 menunjukkan litar yang mengandungi transistor yang digunakan

untuk mengesan suhu cecair. Lampu L akan menyala bila beza keupayaan VBEtapak lebih daripada 3V

Diagram 7.2

Diagram 7.1


7/11

Name the type of transistor used in the circuit in the Diagram 7.2.

Namakan jenis transistor yang digunakan dalam litar dalam Rajah 7.2.

[1mark ](c ) When the light bulbL glows.

Determine the resistance across the resistor R2, when the potential difference

across the thermistor of 1500 is at its maximum.

Bila lampu L menyala.. Cari rintangan melalui perintang R2, bila beza

keupayaan melalui thermistor 1500 adalah pada keadaan maksimum.

[2 marks]

(d) A thermistor of 3200 is used for a liquid so that bulbL will lit at its boiling

point. Table 7.1 shows two possible resistors which can be used as R2.

Termistor 3200 digunakan untuk cecair supaya lampu L akan menyala

apabila mencapai takat didih. Jadual 7.1 menunjukkan dua perintang yang

mungkin digunakan sebagai R2

Resistor Resistance P 1000

Q 1200

Table 7.1

(i) For each of the resistors P and Q, calculate the potential difference

across the Resistor if the resistance of the thermistor is 3200 .

Untuk setiap perintang P dan Q, kirakan beza keupayaan melalui

perintang jika rintangan thermistor adalah 3200 .

[2 marks]


8/11

(ii) Based on your answer in c (i), which resistors can be used as R2?.

Explain your choice briefly.

Berdasarkan jawapan anda di c(i), perintang manakah yang boleh

digunakan sebagai R2. Jelaskan pilihan anda secara ringkas.

[2 marks]

(iii) Why the light bulb L will glow?

Mengapakah lampu L akan menyala?

[1 marks]

8. Diagram 8 shows a system used in a factory to ensure thickness of paper is uniform.

Rajah 8 menunjukkan satu system yang digunakan di sebuah kilang membuat

kertas untuk memastikan ketebalannya adalah sekata.

Diagram 8 /Rajah 8

The radioactive source, radiation detector and counter are used to detect the thickness

of paper. The radioactive source contains a radioisotope. B particle is radiated.

Sumber radioaktif, pengesan sinaran dan pembilang digunakan untuk mengesanketebalan kertas. Sumber radioaktif itu mengandungi radioisotop. Zarah B

dipancarkon.

(a) What is meant by a radioisotope?

Apakah yang dimaksudkan dengan radioisotop?

[I mark]/[l markah]

(b) (i) What is a B particle?

Apakah sebenarnya zarah?

..

[1 mark]/[1 markah]


9/11

(ii) State one detector suitable used for this purpose.

Nyatakan satu alat pengesan yang sesuai digunakan untuk tujuan ini.

[I mark]/[l markah]

(c) Explain why the following radiation is not used.Terangkan mengapa sinaran berikut tidak digunakan.

(i) Alpha particle

zarah alfa

[1 mark]/[1 markah]

(ii) Gamma ray

sinar Gama

[1 mark]/[1 markah](d) What is the container used to keep the radioactive source?

Bekas apakah yang digunakan untuk menyimpan sumber radioaktif.

[1 mark]/[1 markah]

(e) Table 8 shows reading of the rate meter for 3 position at the papers through

detector and radioactive source ?.

Jadual 8 menunjukkan bacaan meter kadar bagi 3 bahagian pada kertas yang

melalui pengesan dan sumber radioaktif

Paper/ kertas P Q R

Rate meter reading/

Bacaan meter kadar

(count per minute/

Bilangan per minit)

370 295 290

(i) Which position shows least thickness?

Bahagian yang manakah menunjukkan ketebalan yang tidak cukup?

[1 mark]/[1 markah]

(ii) State your reason for the answer in 8(e)(i).

Nyatakan .sebab jawapan anda di 8(e)(i).

..



10/11

(f) Now, the paper and radioactive sources are removed.

Sekarang, kertas dan sumber radioaktif dikeluarkan.

(i) What can you observe at the rate meter reading?

Apakah yang dapat diperhatikan pada bacaan meter kadar?

[1 mark]/[1 markah]

(ii) State your reason for the answer in 8(f)(i).

Nyatakan sebab jawapan anda di 8(f)(i)


MARKING SCHEME


11/11

NO ANSWER MARKS

7 a i. Process of adding a certain amount of specific impurities(dopants) to a semiconductor to increase conductivity

ii. Holes as majority carriers

1

1

b N-p-n transistor 1

c 12 3 = 9 VR2 = 9 V1500 3 V

= 500

1

1

d i. Rp RQRp + Rt RQ + RT

1000 x 12 12001000 +3200 1200 + 3200=2.89 V = 3.27 V

ii. QBecause VQ is more than 3 V

iii. there is a current flow

1

1111

8 a The unstable isotopes which decay and gives out radioactive emissions. 1b i. Radioactive ray that emit beta particles

ii. Geiger muller tube11

c i. alpha lose energy faster as they move through mediumii. gamma has a very high penetrating (low ionization )power and

cannot be count.

11

D plumbum 1

E i. Pii. The count in the rate meter is the highest

The thinner the paper, the higher the count in the rate meter

111

f i. The reading in the rate meter will be very highii. less energy loseiii.

111

Trial Physics 2012

Documents

Transcript of Trial Physics 2012