FORM FOUR PHYSICS NECTA 2009

THE UNITED REPUBLIC OF TANZANIA NATIONAL EXAMINATIONS COUNCIL

CERTIFICATE OF SECONDARY EDUCATION EXAMINATION 031/1

PHYSICS 1

(For Both School and Private Candidates)

TIME: 3 Hours Thursday 15thOctober 2009 a.m.

Instructions

1.This paper consists of sections A, B and C.

2.Answer all questions in sections A and B and two (2) questions from section C.

3.Electronic calculators are not allowed in the examination room.

4.Cellular phones are not allowed in the examination room.

6.Where necessary the following ants may be used.

Acceleration due to gravity, g = 9.8ms-2

SECTION A

1. For each of the items (i) - (x), choose the correct answer from among the given alternatives and write its letter beside the item number.

(i)Relative humidity is defined as:

1. the percentage saturated vapour pressure of water at dew point.
2. the percentage of the volume of the water in air required to saturate it at the same temperature.
3. the percentage of moisture in air.
4. the percentage of the mass of water vapour actually present in a unit volume of air required to saturate it at the same temperature.
5. the percentage of the volume of water in air at S.T.P.

(ii)A rod is brought close to the cap of a charged electroscope causing the leaves of the electroscope to collapse. This indicates that:

1. the rod and the electroscope must be oppositely charged.
2. the rod and the electroscope must have the same charge.
3. the rod must be uncharged.
4. the rod may have an opposite charge to the charge on the electroscope or may be uncharged.
5. the rod must be charged.

(iii) A pin-hole camera gives a sharp image:

1. because the image is small
2.  if the hole is small
3.  if the hole is extremely small
4.   because the object is a long way from the hole
5.  because the screen is in a short distance from the hole

(iii) A pin-hole camera gives a sharp image:

1. because the image is small
2. if the hole is small
3. if the hole is extremely small
4. because the object is a long way from the hole
5. because the screen is in a short distance from the hole

(v) What happens when a liquid changes into gaseous state?

1. Some surface molecules absorb latent heat of vaporization and escape.
2. It gives its own latent heat that can be used to heat up the surrounding.
3. The potential and kinetic energies of the molecules increase.
4. The molecules attractive forces to one another increase and their average kinetic energy decreases.
5. There is no adhesive force between molecules.

(vi)    The electromotive force of a dry cell is derived from chemical reaction of:

1. ammonium chloride jelly
2. the powdered carbon
3.   carbon rod and zinc can
4.   manganese dioxide powder
5.  the brass cap

(vii)    What do you find when conducting an experiment of expansion of solids, liquids and gases at the same temperature change?

1.  Solids and gases expand at the same rate.
2. Solids expand more than liquids and gases.
3. Liquids expand more than gases and solids.
4.  Gases expand more than solids and liquids.
5. All expand at the same time.

(viii)Ocean tides are caused by

1.  rotation of the earth about the sun
2. rotation of the moon about the earth
3. gravitational force of the earth on the moon
4.  rotation of the earth about its axis
5. gravitational force of the moon on sea water.

(ix)     In electromagnetic induction:

1.  induced e.m.f is produced wherever a conductor carrying an  electric current has its magnetic flux changed.
2. speed of motion determines direction of the induced current.
3.  Lenzs law gives direction of induced e.m.f
4. induced e.m.f opposes its production methods.
5.  Faradays law gives direction of induced e.m.f

(x)The nuclear reaction   is one which can be used in power generation. In this case the values of x and y are:

1. α and 4n
2. n and 2n
3. γ and n
4.  ß and n
5. e and n

2. Match the items in List A with the responses in List B by writing the letter of the correct response beside the item number.

 LIST A LIST B (i)Surface tension effect (ii)Maximum displacement pendulum bob (iii)Cooling by evaporation (iv)Thermopile (v)Impulse (vi)Tesla (vii)Ferromagnetism (viii)Geiger-Muller counter (ix)Snell's law (x)Voltage amplification A resistor connected to the output circuit  Floating object displaces its own weight Frequency of oscillation Refractive index Bar magnet SI unit of magnetic flux Amplitude A property of solid materials that are strongly affected by magnetism  Solid-state detector Detects radiant energy Product of force and time Radioactive element Capacitor connected parallel to the resistor in the emitter. Detects radioactive radiations SI unit of magnetic flux density Floating without wetting Dogs hang out their tongues during hot weather. Materials that are attracted by a strong magnetic field Depends on the boiling temperature  Force of attraction between liquid molecules

SECTION B

3.(a) Define the following terms:

(i)Force

(ii)Pressure

(b) (i) Briefly explain, when does a force become weight?

(ii) A car of mass 1200kg is brought to rest by a uniform force of 300N, in 80sec. What was the speed of the car?

(c) A rectangular log of wood of density 200kg/m3 has dimensions: 0.3m x 6.0m.

(i)Calculate the maximum pressure it can exert on the ground. How is it experienced?

(ii) Calculate the minimum pressure it can exert on the ground. How can this be observed?

4.(å) Explain the following:

(i) Most materials become less dense as the temperature is increased.

(ii) Latent heat of fusion and latent heat of vaporization are 'hidden'.

(b) (i) Mention three differences between temperature and quantity of heat.

(ii) What is the use of a clinical thermometer?

(c) In a mercury centigrade thermometer, the distance between 00C point and 200C point is 4cm. What is the distance between 00C point and 1000C point?

5.(a) (i) Distinguish between spectrum and dispersion of light.

(ii) Draw a diagram to show an angle of deviation when a ray of light passes through an equilateral glass prism.

(b) (i) How does the additive theory of light differ from the substractive?

(ii) What are primary colours and complementary colours in the substractive theory of light?

(c) A converging lens produces an upright image four times the object height. If the focal length is 25cm, find the object distance.

6. (a) (i) Mention two methods of making a semiconductor more conducting.

(ii) Why are the charge carriers in P-type doped semiconductors?

(b) One end of an N-type doped semiconductor is heated.

(i)State what is expected to develop between the heated and the cooled ends.

(ii)Identify the negative end of the two ends.

(c) (i) Explain the property of a semi conducting diode that makes it ideal in the rectification of an alternative current.

(ii) Sketch a graph of voltage against time for half-wave rectification of an alternating current.

7.(a) (i) What is meant by a transformer?

(ii) Why does a transformer work with alternating current (a-c) only?

(b) State two ways in which power is lost in a transformer.

(c) A 240V main transformer has 1000 turns in primary and N turns in the secondary. It is used to supply energy to a 12V, 24W lamp.

(i)How many turns are there in the secondary?

(ii)What is the efficiency of the transformer if the current drawn from 240V supply is 125mA?

8.Define the terms:-

(ii) Mass number

(b) Study the Figure below, then answer the questions that follow:

(i)What does each of the letters represent?

(ii)Suggest a chemical element for symbol E.

(iii)Write the basic differences between the rays represented by symbols B and D.

(c) A radioactive element nucleus M decays into an element N by ß-emission according to the following equation:

(i)Write the values for x and y.

(ii)What is the number of proton in N?

(iii)What are the mass numbers of elements M and N?

SECTION C

9.(a) State the law of flotation.

(b)A piece of cork with volume 100cm3 is floating on water. If the density of the cork is 0.25g/cm3,

(i)Calculate the volume of the cork immersed in the water.

(ii)What force is needed to immerse the cork completely? (Assume mass of lg has weight of 0.01 N)

(c) Ice has a density of about 0.9g/cm3. What fraction of the volume of an iceberg is submerged in water?

(d) (i) Define the term energy.

(ii) A ball of mass 0.2kg is dropped from a height of 20m. On impact with the ground it loses 30J of energy. Calculate the height it reaches on the rebound.

10.(a) (i) What is a transistor?

(ii) How can transistors be connected to form an amplifier circuit?

(b)Draw a fully stabilized common emitter amplifier circuit and explain the function of the components used.

(c) Draw the graphs for the common emitter transistor characteristics.

11.(a) (i) Define thermionic emission.

(ii)What are x-rays?

(iii)Mention two uses of x-rays.

(b)With the aid of a diagram, explain how x-rays are produced.

(c) Draw a well labelled diagram of a cathode ray oscilloscope.

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