Regulates the rate of electron emission hence the brightness on the screen.
joseph rimiru answered the question on January 2, 2018 at 19:59
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An electric bulb is rated ‘240V,100W .It contains a 1m long coiled tungsten wire . When switched on the wire reaches a temperature of...
(Solved)
An electric bulb is rated ‘240V,100W .It contains a 1m long coiled tungsten wire . When switched on the wire reaches a temperature of about 2500 degrees Celsius.
(i) How much energy is given out by the bulb in 1second
(ii) Why is the wire coiled?
(iii) State two properties of tungsten which make it suitable for use in electric bulbs.
Date posted:
January 2, 2018
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Answers (1)
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There are two types of seismic waves produced by earthquakes. They are called P-waves and S-waves. P-waves are longitudinal and S-waves are transverse.(a) Explain...
(Solved)
There are two types of seismic waves produced by earthquakes. They are called P-waves and S-waves. P-waves are longitudinal and S-waves are transverse.
(a) Explain what is meant by the terms longitudinal and transverse.
longitudinal
transverse
(b) State another example of a longitudinal wave, a transverse wave.
Date posted:
January 2, 2018
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Answers (1)
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A bar magnet AB is suspended freely so that it is able to rotate on a horizontal plane. It turns until end B points southwards....
(Solved)
A bar magnet AB is suspended freely so that it is able to rotate on a horizontal plane. It turns until end B points southwards. Explain how the suspended magnet can be used to identify the north pole of another unmarked magnet.
Date posted:
January 2, 2018
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Answers (1)
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A certain wave of frequency 1000 Hz travels a distance of 600 m in 2 seconds. Determine the wavelength.
(Solved)
A certain wave of frequency 1000 Hz travels a distance of 600 m in 2 seconds. Determine the wavelength.
Date posted:
January 2, 2018
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Answers (1)
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A glass rod is brought near the metal cap of a negatively charged electroscope. The observations are made; a metal rod is then brought...
(Solved)
A glass rod is brought near the metal cap of a negatively charged electroscope. The observations are made; a metal rod is then brought near the metal cap of the same electroscope. State what is observed in the two cases.
Date posted:
January 2, 2018
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Answers (1)
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Give a reason why convex mirrors are preferred over plane mirror for use as rear view driving mirrors in cars ...
(Solved)
Give a reason why convex mirrors are preferred over plane mirror for use as rear view driving mirrors in cars.
Date posted:
January 2, 2018
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Answers (1)
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State the effect on the image formed by a pin hole camera of increasing the size of the pinhole and keeping the distance between the...
(Solved)
State the effect on the image formed by a pin hole camera of increasing the size of the pinhole and keeping the distance between the pinhole and object the same.
Date posted:
January 2, 2018
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Answers (1)
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(a) State the Archimedes principle (b) A light wooden block measuring 2cm by 5cm by 10cm floats in water with its length vertical
(Solved)
(a) State the Archimedes principle (1mark)
(b).A light wooden block measuring 2cm by 5cm by 10cm floats in water with its length vertical. If ¾ of its length is submerged determine (density of water =1000kg/m^3)
(i) The density of the wooden block (3 marks)
(ii) The volume of the wooden block remaining above the surface when floating in a liquid of density 900kg/m^3. (3 marks)
(iii) Additional weight required to be placed on the wooden block so as to just submerge in this liquid
(3 marks)
(c) A meteorological weather balloon of volume 1.2m^3 is tied to a rigid support while being filled with helium gas. The mass of the fabric making the weather balloon is 0.3kg.Determine the maximum tension on the string tying the balloon to the rigid support.(density of air = 1.25kg/m^3 and density of helium is 0.18kg/m^3) (4 marks)
Date posted:
January 1, 2018
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Answers (1)
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Give a reason why a body moving around a vertical or horizontal circle accelerates yet its speed remains constant ...
(Solved)
Give a reason why a body moving around a vertical or horizontal circle accelerates yet its speed remains constant.
Date posted:
January 1, 2018
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Answers (1)
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A syringe contains 100 cm^3 of air at atmospheric pressure. The atmospheric pressure is 1.0 × 10^5 Pascal. The open end of the syringe is...
(Solved)
A syringe contains 100 cm^3 of air at atmospheric pressure. The atmospheric pressure is 1.0 × 10^5 Pascal. The open end of the syringe is sealed and the piston is pushed inwards until the air occupies a volume of 40 cm^3.The temperature of the air remains constant. Calculate the new pressure of the air in the syringe.
Date posted:
January 1, 2018
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Answers (1)
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A box is lying on the floor of a fast moving truck; it is observed that when the lorry is suddenly brought to rest,...
(Solved)
A box is lying on the floor of a fast moving truck; it is observed that when the lorry is suddenly brought to rest, the final position of the box is nearer to the lorry than before. Explain this observation.
Date posted:
January 1, 2018
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Answers (1)
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State three differences between the eye and the camera
(Solved)
State three differences between the eye and the camera.
Date posted:
December 29, 2017
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Answers (1)
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Explain how thunder and lightning is produced during rainstorm.
(Solved)
Explain how thunder and lightning is produced during rainstorm.
Date posted:
December 29, 2017
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Answers (1)
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Ether is put in a beaker which is placed on a thin film of water. A student blows the ether through a pipe continuously, state and...
(Solved)
Ether is put in a beaker which is placed on a thin film of water. A student blows the ether through a pipe continuously, state and explain the observation made after some time.
Date posted:
December 18, 2017
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Answers (1)
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It is observed that during a total eclipse of the sun, both light and heat disappear simultaneously. Explain the observation
(Solved)
It is observed that during a total eclipse of the sun, both light and heat disappear simultaneously. Explain the observation.
Date posted:
December 14, 2017
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Answers (1)
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An n-type semiconductor is obtained when germanium crystal is doped with arsenic. Explain how this change occurs. (N/B. Number of electrons in the outer...
(Solved)
An n-type semiconductor is obtained when germanium crystal is doped with arsenic. Explain how this change occurs. (N/B. Number of electrons in the outer most shell for germanium = 4, and arsenic = 5
Date posted:
December 14, 2017
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Answers (1)
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What is meant by an extrinsic semiconductor?
(Solved)
What is meant by an extrinsic semiconductor?
Date posted:
December 14, 2017
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Answers (1)
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Explain how doping produces an n-type semiconductor for a pure semiconductor material
(Solved)
Explain how doping produces an n-type semiconductor for a pure semiconductor material.
Date posted:
December 14, 2017
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Answers (1)
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Explain why one feels colder when walking on a concrete floor than on a wooden carpet
(Solved)
Explain why one feels colder when walking on a concrete floor than on a wooden carpet.
Date posted:
December 13, 2017
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Answers (1)
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A pure sample of silicon can be changed into p-type semi conductor by adding an impurity. Explain how this is achieved.
(Solved)
A pure sample of silicon can be changed into p-type semi conductor by adding an impurity. Explain how this is achieved.
Date posted:
December 12, 2017
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Answers (1)