PHYSICS – WAVES – TOPICAL QUESTIONS.

FORM FOUR.

 The following constants may be useful

a)                  Acceleration due to gravity, g = 10m/s² or 10N/kg

b)                  Velocity of sound wave in air, V = 330m/s

c)                  Velocity of light, c = 3 10⁸ m/s

3. For each of the items (i) – (x), fill in the blank spaces by writing the correct answer on the space provided.

1. The timbre of sound is also referred to as________________
2. The combination of multiple echoes in the listener’s ear produce a louder and more sustained sound called_________________
3. _____________ is the kind of waves in which do not required any material medium to transfer energy.
4. The phenomenon in which wave encounter a boundary through which it cannot pass and bounce back is called___________
5. ___________ is the apparent bend of wave when encounter an obstacle and spread out of the wave when they go through a gap.
6. The audibility range is referred to as____________
7. The range of electromagnetic wave frequencies to which human eyes are sensitive is called______
8. ___________ has a frequency between 10¹² H_z and 10¹⁴ H_z
9. The parts of human ear which are sensitive to particular frequency of vibration is called______
10. When two different crests meat at the same point in the same direction results greater amplitude than individual, this refers as____________

SECTION B:

Answer all questions.

4. (a) Define Ection.

    (b) Name any two factor that affect the speed of sound in air.

    (c) Explain briefly why sound produced in a hall with many people is heard more clearly than when the hall has few people.

    (d) A person standing 99m from the foot of mountain claps his hands and hears an echo 0.6second  later. Calculate the speed of sound in air.

5. (a) (i) In a longitudinal waves, the particles vibrate to and for forming region of compressions and rarefactions.

               Explain the terms compressions and rarefactions.

 (ii) State the principle of super position.

    (b) (i) State two differences between mechanical waves and electromagnetic waves.

          (ii) Calculate the wavelength of green light of frequency 5.0 10¹⁴ H_z.

    (c) A stretched string has a fundamental frequency of 600Hz. Determine the new frequency if the tension is doubled and its length is halved.

6. (a) Define

1. Amplitude
2. Periodic time

    (b) In a closed pipe, the first resonance is at 23cm and second at 73cm. Determine the wavelength of the sound and the End correction.

7. (a) What is meant by the following terms?

1. Resonance
2. Overtones

    (b) Briefly explain the following.

 (i) The fundamental frequency may alter during the day.

 (ii) Notes of  the same pitch played on violin and a flute sound different.

    (c) The frequency obtained from a plucked sting is 400Hz when the tension is 2N. Calculate:

 (i) The frequency when the tension is 8N.

 (ii) The tension needed to produce a note of frequency 600Hz.

8. (a) (i) What is a sonometer?

          (ii) Briefly explain when resonance is said to occur?

   (b) Two boys at 200m a part stand on one side of a high vertical cliff at the same perpendicular distance from it. When one fires a gun, the other hears the sound 0.6seconds after the flash and the second sound 0.25seconds after the first sound. Calculate the perpendicular distance of the two boys from the cliff.

  (c) Figure 1 illustrates part of the displacement time graph of a wave travelling across water at a particular place with a velocity of 2m/s. Calculate:-

1. The amplitude
2. The frequency
3. The wavelength.

9. (a) (i) Distinguish between  longitudinal and transverse waves.

          (ii) Explain how beats are formed.

    (b) A light wave is refracted into an optically less medium. What change will occur in:-

1. Frequency
2. Speed
3. Wavelength

   (c) (i) What is an echo?

        (ii) A sound is sent out from the ship and its reflection from the floor of the ocean returns over second later. Assuming that the velocity of sound in water is 1500m/s. How deep is the ocean?

SECTION C.

Answer one question from this section.

10. (a) Explain the following

 (i) Wavelength

 (ii) Frequency for sound.

      (b) The velocity of sound in air is 330m/s. Find the wave length in water of sound wave of frequency 660Hz if the velocity of sound in water is 1.32km/s.

       (c) A sonometer wire of length 40cm between two bridges produces a note of 512Hz when plucked at the mid – point. Calculate the length of the wire that would produce a note of 256Hz with the same tension.

11. (a) A sonometer consists of a tant steel wire fixed between two bridges 100cm a part. Defining the first harmonic (2f), second harmonic (3f), third harmonic (4f) and fourth harmonic (5f0) explain how overtones can be obtained.

12. (a) (i) Define the term fundamental frequency.

            (ii) How does the size of the gap in barrier affect the diffraction of waves?

      (b) (i) State  two ways in which visible light differ from radio waves.

            (ii) List two applications of gamma rays.

      (c) Figure 2 and 3 shows a wave travelling across water. Carefully study it then answer the questions that follows.

Determine:

1. Frequency of the wave
2. Velocity of the wave.

TOPICAL EXAM

ELECTROMAGNETISM

SECTION A.

  Answer all questions in this section.

1. For each of the following items (i) – (ii), choose the correct answer among the given alternatives and write its letter besides the item number in the answer booklet provided.

  (i) In electromagnetic induction.

1.     Induced e.m.f is produced whenever a conductor carrying an electric has its magnetic flux changed.
2.     Speed of motion determines direction of the induced current.
3.     Lenz’s law gives direction of the induced e.m.f.
4.     Induced e.m.f opposes its production methods.
5.      Faradays law gives direction of the induced e.m.f.

(ii) When a current flows downward in a straight vertical conductor the direction of its magnetic fields at a point due north of a wire is:-

1.     Upward
2.     North
3.     East
4.     West
5.      Downward.

(iii) In a simple electric generator, the commentator.

1.     Alternate the current in both direction
2.     Changes the current in both direction
3.     Reverses the magnetic fields.
4.     Provides the electric current in one direction.
5.      Increase the strength of motion.

(iv) What is the main function of step up transformer?

1.     To change a.c to d.c current
2.     To decrease resistance
3.     To increase a.c voltage
4.     To decrease a.c voltage
5.      To increase a.c current.

(v) Lenz’s law can be applied to predict the

1.     Magnitude of back e.m.f in a circuit.
2.     Magnitude of induced current in a circuit
3.     Direction of applied e.m.f across the circuit
4.     Direction of induced e.m.f in a circuit.
5.      Direction of the applied e.m.f within a circuit.

(vi) According to the usual transformer notation, which of the following equations is correct?

(vii) An instrument which consists of a solenoid wound around a soft iron core whose magnetism disappears when the current is switched off is called.

1.     An electromagnet
2.     An electric bell
3.     Magnetic relay
4.     A solenoid
5.      Inductor.

(viii) When a coil is steadily rotated in a magnetic field and its terminals connected to ship rings which are in coutact with carbon brushes, then the output at the brushes is:-

1.     A D.C
2.     AN A.C
3.     Half wave rectified
4.     Full wave rectified
5.      None of the above.

(ix) When Fleming’s L.H.R is applied to a motor the thumb points in the direction of:-

1.     The field
2.     The current
3.     The voltage
4.     The force
5.      Velocity.

(x) An iron nail AB is inserted in a coil of an insulated coil whose ends are connected to the terminals of a dry cell as shown in the figure 1 below.

 The correct way of labeling the poles of the resulting electromagnet is:-

1.     A is N and B is S
2.     A is S and B is N
3.     A and B change alternately between N and S.
4.     A and B are both neutral points.
5.      Both A and B are N.

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

3. For each of the items (i) – (x), fill in the blank spaces by writing the correct answer.

a)               Electromagnetism refers to as_______________

b)               The force experienced by conductor carrying current flows in the same direction is______

c)               Mutual induction referred to as_________
An electrical device consisting of two coils (primary and secondary) where secondary coil would over primary coil on an iron is called___________

d)               ____________ is a low resistance connected parallel to the moving coil galvanometer in order to measure current in amperes.

e)               Alternating current generator is also called______________

f)                Electric motor is___________

g)               ___________in the telephones receiver (ear – peace) used to insure that the same pole facing in the same direction.

h)               Transformer is___________

i)                 Generator refers to________________

SECTION B:

4. (a) What do you understand by the terms

1. Step down transformer
2. Electromagnetic induction.

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

    (c) A transformer has a primary coil of 400 turns and secondary coil of 200 turns.

 (i) If the primary coil is connected to 240V mains, what will be the secondary voltage?

            (ii) Calculate the efficiency of the transformer if the primary current is 3A and the secondary current is 5A.

5. (a) State laws of electromagnetism which determine the direction on of magnetic field in a conductor carrying current

    (b) (i) What is induction coil

          (ii) With the help of a labeled diagram, explain the mode of action of an induction coil.

    (c) State reasons why practical transformer are NOT 100% efficient.

6. (a) (i) What is meant by magnetic flux.

          (ii) Illustrate how the right hand grip rule is used to determine electric current and magnetic field directions.

    (b) (i) Draw the diagram of direct current (d.c) generator showing its important parts.

          (ii) Briefly explain how simple a.c dynamo can be converted to simple d.c dynamo.

7. (a) (i) State Flemings’ left hand rule.

         (ii) With the aid of diagram describe forces on parallel conductors with current flowing in opposite direction.

    (b) With the aid of illustration explain briefly the action mechanism of electric bell.

8. (a) List down two (2) factors that affect the magnitude of induced e.m.f in a moving coil galvanometer.

    (b) (i) Explain how eddy current is produced.

          (ii) How can eddy current be minimized?

    (c) A moving coil galvanometer of 30Ώ resistance which carries a maximum current of 15mA can be converted into an ammeter.

 (i) How can the galvanometer be made to give ampere reading?

      (ii) If the device is to give a 1.5A full scale deflection what value of resistance be required?

9.(a) Draw and label  simple a.c dynamo.

   (b) Explain why an e.m.f is induced in the coil as it rotates.

   (c) (i) Show one of the positions of the coil when the dynamo produces maximum e.m.f.

        (ii) At what position of the coil is the induced e.m.f. zero.

SECTION C.

Answer any one (1) question from this section.

10. (a) (i) List laws of electromagnetic induction.

  (ii) Mention two advantages of a.c generator over d.c generator.

       (b) (i) Briefly explain why the core of a transformer is made of thin layers of metal insulated  from one another.

             (ii) Describe the structure of a step – up transformer and state how it works.

       (c) A transformer with 4800 turns in the primary coil is designed to work from 240V a.c mains to give a supply at 8V in order to ring the bell.

     (i) What would happen if the transformer were connected to 240V d.c mains?

    (ii) Briefly explain why the primary current increases when a bell is being rung?

11. (a) (i) What is meant by the terms electromagnetic inductor?

  (ii) List down applications of electromagnetic.

      (b) (i) Why does transformer work with alternating current only.

  (ii) State two (2) 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 coil?

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

RADIOACTIVITY

TOPICAL EXAM.

SECTON A

1. For each of the items (i) – (ii), choose the correct answer among the given alternatives and write its letter besides the item number in the answer booklet provided.

      (i) There are three types of radiation emitted when an unstable atom undergoes radioactive decay, these are:-

1. Uranium, radium, and alpha particle.
2. Proton, radium and electron.
3. Alpha particles, beta particle and gamma rays.
4. Proton, neutron and electron.
5. Alpha particle, proton and atom.

      (ii) If half life of a sample containing 400g of iodine is 8days. The amount of iodide remain undecayed after 400days is

1. 50g
2. 200g
3. 12.5g
4. 80g
5. 20g

     (iii) Which of the following radiations can be absorbed by a metal plate?

1. Alpha (x) particle
2. Gamma rays
3. Beta (B) particle
4. X – rays
5. Cathode rays.

     (iv) The device used to detect radiations from instable nuclei is

1. A ballistic galvanometer
2. An amplifier
3. The decade comiter
4. A Geiger muller tube
5. The carbon 14

      (v) If  A is a mass number, Z is atomic number and N is number of neutrons, identify the correct statement about nuclear decay.

1. When gamma (r) ray emission occurs A and Z remain unchanged.
2. Beta (B) particle emissions are common in the nuclei with N greater than Z.
3. Nuclear decay aims at making Z equal to N.
4. Nuclei with N greater than Z decay by neutron emission.
5. Alpha (x) particle decay occur mainly in heaviest nuclei.

      (vi) One use of gamma – rays (r – rays) is to

1. Treat neurotic
2. Treat black spots
3. Heat fractures
4. Kill cancer cells
5. Join broken hands.

          (vii) The nuclear reaction ₉₂²³⁸U + x                 ₅₆¹⁴⁴Ba + ₃₆⁹⁰K + 1 is one which can be used in power generation. In this case the values of x and y are.

1. x and 4n
2. n and 2n
3. r and n
4. B and n
5. e and n.

          (viii) Which of the following particles is used to cause fission in an atomic reaction.

1.                              Proton
2.                              Deuteron
3.                              Neutron
4.                              Beta – particle
5.                               Alpha particle.

          (ix) Half life of a certain radioactive element is 12 hours. What fraction of an element will have disintegrated in 72hours?

          (x) The mass of an atom depends on the number of

1.                                       Protons only.
2.                                       Neutrons, electrons and protons
3.                                       Electrons and protons
4.                                       Neutrons and protons
5.                                        Electrons and neutrons

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

3. For each of the items (i) – (x), fill in the blank space by writing the correct answer.

1.                                   ___________is a scientific method which is used to determine age of dead living and non – living organisms.
2.                                   Nuclear fission referred to as___________
3.                                   The emission of radiations due to the bombarding a small and stable nuclei by high energetically particles is called__________
4.                                   The particle with low penetrating power and has biggest mass is known as___________
5.                                   Binding energy can be defined as__________________
6.                                   ____________ is the energy or particle or electromagnetic waves emitted by ustable atom.
7.                                   One of the application of nuclear fusion is___________
8.                                   The device used to detect the pressure of radiation base on their ability to ionize dry air molecules by producing sparks is called______________
9.                                   The emission of radiation due to bombarding small and stable nuclei by high energetically particles is called___________
10.                                   New atom formed after disintegration of heavier nuclei is called____________

SECTION B:

 Answer all questions

4. (a) What are:-

(i) x – particles

(ii) B – particles

(iii) r – rays

     (b) A radon nucleus ₈₆²²²Rn emits an x – particle followed by B – particles. What are the atomic number and mass number of the nucleus formed after the emission?

     (c) A radioactive source has a half – life of 16 days. How long will it take for the count to fall from 160 per minute to 20 per minute.

5. (a) Explain the terms fission and fusion for nuclei.

    (b) Identify the three radiations products of radioactive nuclei.

    (c) Write three properties of x – particles.

    (d) (i) What is the importance of radioactivity in organic matter.

          (ii) How is nuclear fusion important to life?

6. (a) Explain how radioactivity differs from any type of chemical reaction.

    (b) A radioactive element has a half – life of 3minutes. If the initial count rate is 512 per minute, how long does it take to reach a count rate of 64 per minute? What fraction of  the original element is left?

7. (a) Name two instruments which are used to detect radiation from radioactive sources.

    (b) Write down three simple tests you would carry out in the laboratory in order to identify the three radioactive radiations, x, B and r.

    (c) A uranium nucleus U₂₄₈ with atomic number 92 emits two x – particles and two B – particles and finally forms a thorium (Th) nucleus.

  (i) Write the reaction equation which describes the above process.

  (ii) Determine the mass number and atomic number of thorium (Th).

8. (a) Complete the table below for the three particles which are emitted in nuclear decay process.

      (b) Part of a certain nuclear decay series is represented by the following unbalanced equations in each stage only ONE type of a particle is emitted.

 (i) ₉₀Th²³² ₈₈Ra²²⁸

 (ii) ₈₈Ra²²⁸                          ₈₉Ac²²⁸

 (iii) ₈₈Ac²²⁸                                ₉₀Th²²⁸

 (iv) ₉₀Th²²⁸                              ₈₈ Ra²²⁴

 Identify the type of particles emitted in each of the above stages.

     (c) Write half life of a certain radioactive substance is 64 days. Explain the meaning of this statement.

     (b) A certain  radioactive material has a half – life of 2 minutes. If the initial count rate is 256 per minute.

 (i) How long does it take to reach a count rate of 32 per minute?

 (ii) What fraction of the original number of atoms is left undecayed?

     (c) A certain radioactive material is denoted by the symbol ₈₈²²⁶X. Write down the composition of the nucleus during the end of the following stages of disintegration.

 (i) The emission of an x – particle

 (ii) The further emission of B- particle

 (iii) The further emission of r – radiation.

SECTION C.

 Answer one question from this section.

10. (a) Define the following terms.

 (i) Binding energy

 (ii) Thermonuclear fusion.

       (b) (i) What is meant by background count? Give two sources of radiations always present in   a neighborhood of a detector.

 (ii) How does the rate of escape of electrons from a metal relate to its temperature?

 (iii) A sample containing 400g of iodine – 131, has a half life of 8days. How much of the sample will remain undecayed after 40 days?

11. (a) (i) What are the dangers in handling radioactive material?

           (ii) What are the precautions to be taken in order to reduce the dangers mentioned in 11 (a) (i) above in research laboratories?

      (b) Hospital blankets have to be sterilized after use on the bed of a patient with infectious diseases. Radiation sterilization is used nowadays because blankets wear out quickly with steam sterilization. What type of radiation would be suitable?

TOPICAL EXAMINATION

GEOPHYSIC

SECTION A

1. Multiple choice questions

 (i) Which of these is not a feature of continental crust?

1.               Extends to a depth of 2900km
2.                It has  a low density
3.                Mainly composed of granite and sedimentary rocks
4.               Land mass and mountain are found here.

(ii) The boundary that separates core and mantle is called? 

1.               Mahorovic discontinuity
2.                Gotten berg discontinuity
3.                Thermal zone
4.               Mantle layers.

(iii) Region of atmosphere nearest to earth is called?

1.               Stratosphere
2.                Mesosphere
3.                Troposphere
4.               Thermosphere

(iv) Which region of atmosphere has ozone layer?

1.               Mesosphere
2.                Stratosphere
3.                Tropopouse
4.               Troposphere

(v) Which of the following gases is not found in atmosphere?

1.               Nitrogen
2.                Oxygen
3.                Carbon dioxide
4.               Hydrogen

(vi) A kind of Tectonic boundary where two plate sides moving each other without coming together is called?

1.               Opposing boundary
2.                Conservative  boundary
3.                Constructive boundary
4.               Destructive boundary

(vii) An example of active volcano is?

1.               Mt. Longonot
2.                Mt. Kenya
3.                Mt. Oldonyo Lengai
4.               Mt. Kilimanjaro

(viii) Energy released by earth – quakes from the centre is called?

1.               Seismometer
2.                Tidal energy
3.                Seismic wave
4.               Hypocenter energy.

(ix) Which of the following is not a feature of surface wave?

1.               It compresses waves
2.                It is shear wave
3.                It longitudinal wave
4.               First detected seismic stations.

(x) Which of the following is an earth quake warming sign?

1.               Thermal indictors
2.                Water indicator
3.                Seismo – electromagnetic indicator
4.               All of the above.

2. Match the following items

SECTION B

3.                Draw a cross section of the earth’s interior region and shown:

a)     The crust.

b)     The mantle.

c)      The outer core.

d)     The inner core.

4.                Explain why the inner core of the earth is solid while the outer core is liquid even thought the temperature is high.
5.                Explain how volcanoes occur.
6.                The diagram below shows the structure of a volcano. Label the parts marked A, B, C and D.
7.                What is earthquake?
8.                Explain the meaning of the following terms as used in earth quakes: i) hypocenter ii) epicenter.
9.                Name the instrument used to measure earthquakes.
10.           Give five hazards associated with earthquakes.
11.           List down three precautions that can be taken against earthquake hazards.
12.           List down the various layers of the atmosphere starting from the earth’s surface.
13.           Give one importance of each of the layer of the atmosphere.
14.           What is the ionosphere?
15.           What is global warning?
16.           Name four gaseous that contribute to global warming and give one source of each.
17.           Give four effects of global warming.

TOPICAL EXAMINATIONS

FORM FOUR ELEMENTARY ASTRONOMY

SECTION A.

1 . Which of the following is NOT a general difference between a planet and a star? 

A. Planets are smaller than stars. 

B. Planets are dimmer than stars. 

C. All planets are made of rock and all stars are made of gas. 

D. Planets orbit stars, while stars orbit the center of the galaxy. C

2 . Our solar system consists of _________. 

A. the Sun and several nearby stars, as well as the planets and other objects that orbit these stars 

B. the Sun and all the objects that orbit it 

C. a few hundred billion stars, bound together by gravity 

D. the Sun and the nine planets, and nothing else B

3 . A typical galaxy is a _________. 

A. system consisting of one or a few stars orbited by planets, moons, and smaller objects 

B. nearby object orbiting a planet 

C. large, glowing ball of gas powered by nuclear energy 

D. collection of a few hundred million to a trillion or more stars, bound together by gravity 

E. relatively small, icy object orbiting a star D

4 . Which of the following best describes what we mean by the universe? 

A. A vast collection of stars that number as many as the grains of sand on all the beaches on

Earth 

B. All the galaxies in all the super clusters 

C. The sum total of all mater and energy 

D. The universe is another name for our Milky Way Galaxy. C

5 . What do astronomers mean by the Big Bang? 

A. The event that marked the beginning of the expansion of the universe 

B. The explosion of a massive star at the end of its life 

C. A gigantic explosion that blew all the galaxies in the universe to smithereens 

D. The event that marked the birth of our solar system A

6 . What do we mean when we say that the universe is expanding? 

A. Everything in the universe is gradually growing in size. 

B. The statement is not meant to be literal; rather, it means that our knowledge of the universe is growing. 

C. Average distances between galaxies are increasing. 

D. Average distances are increasing between star systems within galaxies. C

7 . Based on observations of the universal expansion, the age of the universe is about

_________. 

A. 14,000 years 

B. 14 trillion years 

C. 14 billion years 

D. 14 million years C

8 .  A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________. 

A. a light-year is an astronomically large unit, so a product could not possibly be so advanced 

B. light-years can only be used to talk about light 

C. it uses "light-years" to talk about time, but a light-year is a unit of distance 

D. it doesnt specify the number of light-years C

9 . The term observable universe refers to _________. 

A. the portion of the universe that is not hidden from view by, for example, being below the horizon 

B. that portion of the universe that we have so far photographed through telescopes 

C. the portion of the universe that can be seen by the naked eye 

D. that portion of the universe that we can see in principle, given the inite age of the universe D

10 . On a scale in which the distance from the Sun to the Earth is about 15 meters, the               distance from the Earth to the Moon is _________. 

A. small enough to it within your hand 

B. about 5 meters 

C. about 30 meters 

D. about 1 meter A

11. Match the following items;

SECTION B

12. (a) (i) Define the term astronomy and asteroids

             (ii) Is scorpion a galaxy or constellations? Give reason(s) for your answer

             (b) Distinguish between;

• Planet and star
•  Comet and meteor

             (c) Which planet in the solar system is;

• Closest to the sun? (mercury)
• Furthest from the sun? (pluto)
•  Closest to the earth? (venus and mars)
• Surrounded by ring? (saturn)
•  The second largest planet? (saturn)

13.  What is solar system?

14.  How many known planets are there in our solar system? Name them.

15.  Why is Pluto not a planet as it used to be?

16.  Which planets in the solar system have satellites?

       17. What is a moon?

               b) Briefly explain the properties of a moon

       18.  What are oscillations?

                 b) Give the two types of oscillations

        19. Explain the importance of learning astronomy

TOPICAL EXAMINATION

FORM FOUR ELECTRONICS

SECTION A.

1. The voltage gain in a transistor connected in ………………. arrangement is the highest

1. common base
2. common collector
3. common emitter
4. none of the above

2. As the temperature of a transistor goes up, the base-emitter resistance ……………

1. decreases
2. increases
3. remains the same
4. none of the above

3. The most commonly used semiconductor is ………..

1. Germanium
2. Silicon
3. Carbon
4. Sulphur

4. When a pure semiconductor is heated, its resistance ………….. 

1. Goes up
2. Goes down
3. Remains the same
4. Can’t say

5. The strength of a semiconductor crystal comes from ……..

1. Forces between nuclei
2. Forces between protons
3. Electron-pair bonds
4. None of the above

6. An n-type semiconductor is ………

1. Positively charged
2. Negatively charged
3. Electrically neutral
4. None of the above

7. As the doping to a pure semiconductor increases, the bulk resistance of the semiconductor ………..

1. Remains the same
2. Increases
3. Decreases
4. None of the above

8. A pn junction acts as a ……….

1. Controlled switch
2. Bidirectional switch
3. Unidirectional switch
4. None of the above

9. The term bias in electronics usually means ……….

1. The value of ac voltage in the signal.
2. The condition of current through a pn junction.
3. The value of dc voltages for the device to operate properly.
4. The status of the diode.

10. Transistor biasing is done to keep ………… in the circuit

1. Proper direct current
2. Proper alternating current
3. The base current small
4. Collector current small

SECTION B

11. Describe the effect of temperature on conductors and insulators,

12. Explain the difference between conductors, semiconductors and insulators using the energy band concept.

13. What is doping?

14. Explain the mechanism of doping.

15. What is a p-n junction?

16. Explain the mode of action of p-n junction.

17. List down two types of diodes.

18. Draw a circuit diagram to show half wave and full wave rectification.

19.  What is a transistor?

20. Draw a diagram of a p – n – p transistor and explain its mode of action,

21. List down two applications of transistors.

22.  (a)    List down the applications of transistors. 

        (b)    Draw a circuit diagram to show half wave and full wave rectifications. 

        (c)     Explain the difference between conductors, semiconductors, and insulators    using the energy band concept. 

23.  (a) Define capacitance of a capacitor. 

        (b) A capacitor labeled with a capacitance of value of   is charged to a potential   difference of 10V. Calculate the charge stored by the capacitor. 

        (c) After a long flight a plane may be charged. 

      (i) What causes the charge. 

     (ii) Why an attendant who will immediately opens the door from outside after   the landing of plane is at risk?