HomeExamination QuestionsPHYSICS FIRST TERM EXAMINATION SS 3

PHYSICS FIRST TERM EXAMINATION SS 3

FIRST TERM

 

Examination malpractices may lead to a repeat of the subject or suspensions don’t be involved.

SUBJECT: PHYSICS                       TIME: 2HRS            CLASS: SS  3

SECTION A (OBEJECTIVES)

Instruction: Answer ALL questions in this section. All question carry equal mark

Constants: Unless otherwise stated, used these constants (c=3.0×108 ms-1, e = -1.6×10-19C, Me = 9.1×10-31kg, take 1/4πɛ◦=9.0×109, G= 6.67×10-11Nm2kg-2, g=10m/s2)

  1. Which of the following radiation is of nuclear origin? (a) X- rays (b) Visible –rays (c) Radio waves (d) Gamma rays
  2. A satellite is in a parking orbit if its period is (a) equal to the period of the earth (b) less than the period of the earth (c) the square of the period of the earth (d) more than the period of the earth
  3. The magnitude of the gravitational attraction between the earth and a particle is 40N. if the mass of the particle is 4kg, calculate the magnitude of the gravitational field intensity of the earth on the particle (a) 10.0Nkg-1 (b) 12.6Nkg-1 (c) 25.0Nkg-1 (d) 160.0Nkg-1
  4. The potential difference across a parallel plate capacitor is 500V while the charge on either plate is 12μC. Calculate the capacitance of the capacitor (a) 6.0×10-3F (b) 2.4×10-4F (c) 6.0×10-5F (d) 2.4×10-8F
  5. The net capacitance in the circuit below is(a) 8.0μF (b) 6.0μF (c) 4.0μF (d)2.0μF

2μF

P                                                          4μF

 

 

2μF

  1. Which of the following statement is not true? (a) the chemical action in a primary cell is irreversible (b) lead-acid accumulation can be recharged (c) lead-acid accumulator has large internal resistance (d) a secondary cell can be recharged
  2. As the plates of a charged variable capacitor are moved closer together, the potential difference between them (a) increases (b) decreases (c) remains the same (d) is doubled
  3. The defect in simple cell which result in a back e.m.f. and increase in internal resistance is known as (a) local action (b) reduction (c) polarization (d) oxidation
  4. Which of the following statement about the defects of simply cells is not correct? (a) Polarization defect is minimized by use of manganese oxide as depolarizer (b) Polarization may also be reduced by brushing the plates occasionally (c) Local action occurs because zinc is not pure (d) Local action
  5. The electrochemical equivalent of a metal is 0.126×10-6kgC-1. The mass of the metal that a current of 5A will deposit from a suitable bath in 1hour is (a) 2.268×10-3kg (b) 0.378 x10-3kg (c) 0.0378 x10-3kg (d) 0.227 x10-3kg
  6. The electrochemical equivalent of platinum is 5×10-7kgC-1. To plate-out 1.0kg of platinum, a current of 100A must be passed through an appropriate vessel for (a) 5.6hours (b) 56hours (c) 1.4×104hours (d) 2.0×104hours
  7. A wire of 5Ω resistance is drawn out so that its new length is twice the original length. If the resistivity of the wire remains the same and the cross-sectional area is halved, the new resistance is (a) 5Ω (b) 10Ω (c) 20Ω (d) 40Ω
  8. A cell of e.m.f. 1.5V and internal resistance 2.5ohms is connected in series with an ammeter of resistance 0.5 ohms and a resistor of resistance 0.7ohms. Calculate the current in the circuit (a) 6.67A (b) 0.20A (c) 0.60A (d) 0.15A
  9. If the angle of declination in a place is 00, calculate the true geographic bearing if the compass needle reads N400E (a) N500E (b) N400E (c) N300E (d) N250E
  10. A magnetic substance can be demagnetized by? (a) Dropping on the floor (b) hammering while red hot (c) divided touch (d) single touch
  11. A freely suspended needle compass needle on earth’s surface will come to rest in a plane called (a) geographic equator (b) geographic meridian (c) magnetic equator (d) magnetic meridian
  12. To convert an alternating current dynamo into a direct current dynamo, the (a) the number of turns in the coil is increased (b) strength of the field magnet is increased (c) slip rings are replaced with split ring commutator (d) coil is wound on a soft iron armature
  13. A transformer with 5500 turns in its primary is used between a 240V a.c. supply and a 120V kettle. Calculate the number of turns in the secondary (a) 2750 (b) 460 (c) 11,000 (d) 232
  14. Energy losses dues to eddy currents are reduced by using (a) low resistance wires (b) insulated soft iron wires (c) few turns of wire (d) high resistance wires
  15. An object of mass 12kg is held at a height of 5m above the ground for 30 seconds. The work done within this period is (a) 600J (b) 200J (c) 60J (d) 0J
  16. An object having a mass 40kg will experience a gravitational force of 68N on a planet on which the intensity of the gravitational field is (a) 0.4 Nkg-1 (b) 1.7 Nkg-1 (c) 9.8 Nkg-1 (d) 2,720 Nkg-1
  17. The mass of a certain planet P is one-hundredth that of the earth while its radius is one-quarter of the earth’s radius. If the acceleration due to gravity on the earth is 10m/s2, then its value on P is (a) 0.10m/s2 (b) 0.40 m/s2 (c) 1.60 m/s2 (d) 2.50 m/s2
  18. The radius of the earth is 6.4x 106m and the acceleration due to gravity is 10m/s2. The escape velocity of a rocket launched from the earth’s surface is (a) 4.2km-1 (b) 4.0 km-1 (c) 11.3 km-1 (d) 25.3 km-1
  19. The electric field strength at a point close to and lying along the axis of a solenoid , will be greatest if the core of the solenoid is made of (a) brass (b) iron (c) copper (d) steel
  20. The angle between the geographic and the magnetic meridians at a point on the earth’s surface is (a) 900 and 00 (b) 00 and 900 (c) 00 and 00 (d) 900 and 900
  21. Which of the following connections will convert a milliameter into a voltmeter? (a) a high series resistance (b) a high parallel resistance (c) a low series resistance (d) a low parallel resistance
  22. The operation of a moving coil is based on (a) electromagnetic induction (b) magnetic effect of electric current (c) force on a current carrying conductor in a magnetic field (d) electrochemical effect
  23. The mouthpiece of a telephone primarily converts sound energy to (a) mechanical energy (b) heat energy (c) electrical energy (d) chemical energy
  24. The peak value of the p.d. in an A.C is 240V. The instantaneous p.d at 1/8th of a cycle is (a) V(b) V (c) 120V (d) 60V
  25. A galvanometer of resistance 38ohms is to be connected in series with a shunt such that 1/20 of the current in the circuit passes through the galvanometer. The shunt resistance required is (a) 1.9ohms (b) 2.0ohms (c) 36.1ohms (d) 38.0ohms
  26. An electric motor powered by a 110v rms supply draws a current of 8A. The motor is used to lift a mass if 50kg through a vertical distance of 5.5m in 5s. If g=10m/s2, the efficiency of the machine is (a) 80% (b) 62.5% (c) 8.0% (d) 6.3%
  27. The primary to secondary transformation ratio in a transformer is 2:3. If the primary is 10kv, the voltage across the secondary is (a) 4kv (b) 5kv (c) 25kv (d) 50kv
  28. If the current in the primary in question 43 is 4A, the current inn the secondary is (a) 10.0A (b) 5.0A (c) 2.5 A (d) 1.6A
  29. Which of the following is associated with alternating currents only? (a) a moving coil galvanometer (b) a transformer (c) a lead-acid accumulator (d) an induction coil
  30. A coil of resistance 30ohms is connected to a 100v, 50/π Hz AC source. If the coil draws rms current 2A, its inductance us (a) 0.40H (b) 0.60H (c) 1.25H (d) 2.50H
  31. If a broadcasting station sends out waves of wavelength 300m. On what frequency is the station operating? (a) 1000KHz (b) 1000Hz (c) 1000mHz (d) 1000MHz
  32. Calculate the capacitance of a parallel plate capacitor with area of plate 0.01m2, with a dielectric of εr=7 and separated by 10mm. ε0=8.85×10-12Fm-1 (a) 62.00 x10-12F (b) 6.205 x10-12F (c) 0.62 x10-12F (d) 0.06 x10-12F
  33. What length of resistance wire of diameter 0.6mm and resistivity1.1×10-6Ωm would be cut in order to make a 44Ω resistor? (a) 1.5Ω (b) 3.0Ω (c) 4.5Ω (d) 6.0Ω
  34. If a current carrying coil is mounted on a metal frame, the back e.m.f. induced in the coil causes (a) inductance (b) eddy current (c) electromagnetism (d) inertia
  35. An equipment that functions a result of the magnetic effect of electric current is (a) rheostat (b) thermostat (c) electric bell (d) carbon microphone
  36. The force on a current carrying conductor in a magnetic field is greatest when the (a) the conductor makes an angle of 600 with the field (b) force is independent of the angle between the field and the conductor (c) conductor is parallel with the field (d) conductor is at right angle with the field
  37. A conductor of length 2m carries a current of 0.8A while kept in a magnetic field of magnetic flux density 0.5T. The maximum force acting on it is (a) 0.2N (b) 0.8N (c) 3.2N (d) 8.0N
  38. The energy stored in an inductor of inductance 5mH when a current of 6A flows through it is (a) 1.4×10-2J (b) 1.8 x10-2J (c) 9.0 x10-2J (d) 1.4 x10-3J
  39. Calculate the r.m.s value of an alternating e.m.f of peak value 220V (a) 150V (b) 156V (c) 160V (d) 166V
  40. In electrolysis, a current I flows for 20 minutes and deposits a mass m of silver on the cathode. A current 2I flowing for 5 minutes will deposit a mass of sliver of (a) 2m (b) 4m (c) m/2 (d) m
  41. A charge of one coulomb liberates 0.0033g of copper in an electrolytic process. How long will it take a current of 2A to liberate 1.98g of copper in such a process? (a) 5 minutes (b) 30 minutes (c) 60 minutes (d) 120 minutes
  42. A cell of emf 2V and internal resistance 1 ohm supplies a current of 0.5A to a resistor whose resistance is (a) 0.5 (b) 1 (c) 2 (c) 3
  43. Two cells each of emf 1.5V and an internal resistance 2ohm are connected in parallel. Calculate the current flowing when the cells are connected to a 1 ohm resistor (a) 0.75A (b) 1.5A (c) 0.5A (d) 1.0A
  44. Electric power is transmitted at a high voltage rather than low voltage because the amount of energy loss is reduced to (a) heat dissipation (b) production of eddy current (c) excessive current discharge (d) excessive voltage discharge
  45. A transformer has primary coil with 500 turns and a secondary coil with 2500 turns. When the voltage input to the primary coil is 120V, the output is (a) 6000V (b) 600V (c) 240V (d) 24V

SECTION B (THEORY)

Instruction: Attempt any THREE questions in this section

  1. (a) The mass of proton is 1.67×10-27kg and the mass of an electron is 9.11×10-31kg, calculate the force of gravitation between: (i) a proton and an electron (ii) two electrons [G= 6.67×10-11Nm2kg-2; distance between the protons = 4.0m; distance between the electrons = 2×10-2m; distance between the proton and the electron = 5.4×10-11m] 4marks

(b) State Newton’s law of universal gravitation     2mark

(c) The primary winding of a transformer has 400 turns and its secondary has 100 turns. If a source of emf of 12V is applied to the primary, calculate the secondary emf                    4marks

  1. (a) Three capacitors having capacitances 0f 5µF, 15 µF and 25 µF respectively are connected in series to a 15v d.c. supply. Calculate the (i) combined capacitance of the capacitor (ii) voltage across each capacitor (iii) energy stored in the 15 µF capacitor 6marks

(b) List and explain the two types of transformer     4marks

  1. (a) An 0.50 uF capacitor, a 30.0 ohm resistor and a 0.050H inductor are connected in series across a voltage source of e.m.f. 50Vrms, 100/πHz. Calculate the values of: (i) capacitive reactance; and (ii) inductive reactance                                    3marks

(b) A galvanometer of resistance 50Ω which gives a full-scale deflection for 1mA is to be adapted to measure currents up to 5A. (i) calculate the resistance of the resistor required (ii) if the resistor is made of a material of cross-sectional area 4×10-4cm2 and resistivity 2×10-6Ωm, calculate its length                                       3marks

(c) The electrochemical equivalent of silver is 0.0012g/c. If 36.0g of silver is to be deposited by electrolysis on a surface by passing a steady current of 5.0 minutes, calculate the quantity of the current needed 4marks

  1. (a) A battery of three cells in series, each of e.m.f. 2 V and internal resistance 0.5 Ω is connected to a 2 Ω resistor in series with a parallel combination of two 3Ω resistors. Draw the circuit diagram and calculate (i) the effective external resistance (ii) the current in the circuit (iii) the lost volts in the battery (iv) the current in one of the 3 Ω         6marks

(b) Calculate the escape velocity of a satellite from the earth’s gravitational filed (g=9.8ms-2, radius of the earth = 6.4×103km) 2marks

(c) What is electric field intensity? 2marks

  1. (a) If a transformer is used to light a lamp rated at 60W, 220V from a 4400V a.c. supply, calculate (i) ratio of the number of the turns of the primary coil to the secondary coil in the transformer (ii) current taken from the mains circuit if the efficiency of the transformer is 95% 3marks

(b) A particle of charge 0.5C moves at a velocity of 2.5m/s in a direction perpendicular to a magnetic field of strength 0.20T. Calculate the magnetic force experienced by the particle.  3marks

(c) Briefly discuss the types of  defects in primary cell           4marks

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