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A transformer has 200 turns in the primary coil and 1000 turns in the secondary coil. The primary coil is connected to an a.c source...
(Solved)
A transformer has 200 turns in the primary coil and 1000 turns in the secondary coil. The primary coil is connected to an a.c source producing 100 V and rated 500 W. The current delivered by the secondary circuit was found to be 0.95 A.
(i) Determine the efficiency of this transformer.
(ii) Explain why the efficiency is less than 100%.
Date posted:
September 6, 2019
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Answers (1)
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A bar magnet is pushed into a coil as shown in the figure below.
(Solved)
A bar magnet is pushed into a coil as shown in the figure below.
Explain what happens to the pointer of the galvanometer when the magnet is:
(i) Moved into the coil rapidly?
(ii) Remains stationary inside the coil?
Date posted:
September 6, 2019
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Answers (1)
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An electric kettle is rated at 1.8 kW, 240 V. Explain the choice of the safest fuse for the kettle. (the available fuses are 5...
(Solved)
An electric kettle is rated at 1.8 kW, 240 V. Explain the choice of the safest fuse for the kettle. (the available fuses are 5 A, 10A, and 20 A)
Date posted:
September 6, 2019
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Answers (1)
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The figure below shows a wave form.Determine the wavelength given that the speed of the wave is 400 m/s.
(Solved)
The figure below shows a wave form.Determine the wavelength given that the speed of the wave is 400 m/s.
Date posted:
September 6, 2019
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Answers (1)
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The range of audible frequencies varies from 20 Hz to 20 kHz. If the speed of sound is 340 m/s, what is the corresponding range...
(Solved)
The range of audible frequencies varies from 20 Hz to 20 kHz. If the speed of sound is 340 m/s, what is the corresponding range of wavelength?
Date posted:
September 6, 2019
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Answers (1)
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The chart below shows part of the electromagnetic spectrum.
(Solved)
The chart below shows part of the electromagnetic spectrum.
(a) Identify the radiation marked A and C.
(b) Give one application of the radiation marked B.
Date posted:
September 6, 2019
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Answers (1)
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The figure below shows a steel bar to be magnetized.
(Solved)
The figure below shows a steel bar to be magnetized.
Complete the circuit such that both poles P and Q acquire opposite polarity (North- south respectively).
Date posted:
September 6, 2019
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Answers (1)
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An object of height 2 cm is placed 25 cm in front of a concave mirror. A real image is formed 75 cm from the...
(Solved)
An object of height 2 cm is placed 25 cm in front of a concave mirror. A real image is formed 75 cm from the mirror.Calculate the height of the image.
Date posted:
September 6, 2019
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Answers (1)
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The figure below shows a ray of light incident on a plane mirror.
(Solved)
The figure below shows a ray of light incident on a plane mirror.
(a) On the diagram, indicate the direction of the reflected ray.
(b) Give a reason for the path shown above.
Date posted:
September 6, 2019
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Answers (1)
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A certain mass of hydrogen gas occupies a volume of 1.6m3 at a pressure of 1.5x105Pa and a temperature of 120c. Determine the volume when...
(Solved)
A certain mass of hydrogen gas occupies a volume of 1.6m3 at a pressure of 1.5x105Pa and a temperature of 120c. Determine the volume when the temperature is 00c at a pressure of 1.0x103
Date posted:
September 6, 2019
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Answers (1)
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A cork of volume 100cm3 is floating on water. If the density of the cork is 0.25 gcm-3 and that of water is 1 gcm-3;
(a)...
(Solved)
A cork of volume 100cm3 is floating on water. If the density of the cork is 0.25 gcm-3 and that of water is 1 gcm-3;
(a) Calculate the mass of the cork
(b) Hence, find the upthrust force on the cork
(c) What minimum force is required to immerse the cork completely
(d) What is the effect on the upthrust force in a liquid when the temperature of the liquid is reduced?
Date posted:
September 6, 2019
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Answers (1)
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In an experiment to determine the specific latent heat of vaporization of water, steam at 100ºC was passed into water contained in a well-lagged copper...
(Solved)
In an experiment to determine the specific latent heat of vaporization of water, steam at 100ºC was passed into water contained in a well-lagged copper calorimeter. The following measurements were made:
- Mass of calorimeter = 60g
- mass of water + calorimeter = 145g
- Final mass of calorimeter + water + condensed steam = 156g
- Final temperature of the mixture = 48oC
[Specific heat capacity of water = 4200JKgˉ¹kˉ¹ and specific heat capacity of copper = 390JKgˉ¹kˉ¹
Determine the;
(i) mass of condensed steam.
(ii) The heat gained by the water and calorimeter if the initial temperature of the calorimeter and water is 20ºC.
(iii) Given that Lv is the specific latent heat of vaporization of steam, write an expression for the heat given out by steam.
(iv) Determine the value of Lv above
(v) State the assumption made in the above experiment
Date posted:
September 6, 2019
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Answers (1)
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The diagram below shows a graph of force against extension for a certain spring.
(Solved)
The diagram below shows a graph of force against extension for a certain spring.
(i) What is the spring constant of the spring?
(ii) What force would cause two such springs placed side by side to stretch by 10cm
Date posted:
September 6, 2019
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Answers (1)
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The height of a mountain is 1360m. The barometer reading at the base of the mountain is 74cmHg. Given that the densities of mercury and...
(Solved)
The height of a mountain is 1360m. The barometer reading at the base of the mountain is 74cmHg. Given that the densities of mercury and air are 13,600Kgm-3 and 1.25Kgm-3 respectively, determine the barometer reading at the top of the mountain.
Date posted:
September 6, 2019
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Answers (1)
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The figure below is a simple hydraulic machine used to raise heavy loads.
(Solved)
The figure below is a simple hydraulic machine used to raise heavy loads.
Calculate;
(i) The pressure exerted on the oil by the force applied at A
(ii) The load raised at B
(iii) Give two properties which make the oil suitable for use in this machine
Date posted:
September 6, 2019
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Answers (1)
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A stone of mass 40g is tied to the end of a string 50cm long such that it is 20m above the ground at its...
(Solved)
A stone of mass 40g is tied to the end of a string 50cm long such that it is 20m above the ground at its lowest level as shown in the diagram below. It is whirled in a vertical circle at 2rev/s.
(i) If the string breaks at its lowest level as shown, what is the velocity with which it travels?
Calculate the maximum tension in the string.
(ii) Calculate the maximum tension in the string.
(iii) Determine the maximum horizontal distance it travels from the breaking point
Date posted:
September 6, 2019
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Answers (1)
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Using Kinetic theory of matter, explain why solids expand when heated.
(Solved)
Using Kinetic theory of matter, explain why solids expand when heated.
Date posted:
September 6, 2019
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Answers (1)
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The figure below shows a machine being used to raise a load.Determine the efficiency of the machine.
(Solved)
The figure below shows a machine being used to raise a load.Determine the efficiency of the machine.
Date posted:
September 6, 2019
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Answers (1)
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The diagram below shows a braking system.Why is the master piston, made smaller than the slave piston?
(Solved)
The diagram below shows a braking system.Why is the master piston, made smaller than the slave piston?
Date posted:
September 6, 2019
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Answers (1)
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The diagram below shows a uniform 5m long metal rod of mass 800g. It is suspended by a string tied at a point 3.5m from...
(Solved)
The diagram below shows a uniform 5m long metal rod of mass 800g. It is suspended by a string tied at a point 3.5m from one end. Determine the load which should be hung at point X to keep the plank horizontal.
Date posted:
September 6, 2019
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Answers (1)