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i) The leaf falls. OR The leaf divergence decreases.
ii) Photoelectrons are emitted from the zinc plate which is negatively charged. The photoelectrons are then repelled by the negative charges on the plate and the electroscope becomes discharged.
iii) The leaf divergence remains unchanged. The photoelectrons emitted do not escape due to attraction by the positive charges on the plate.
Kavungya answered the question on October 30, 2019 at 13:18
- The figure below shows the essential components of an x-ray tube
a)Name the parts labelled A and B.
b)Explain how electrons are produced.
c)During the operation of the...(Solved)
The figure below shows the essential components of an x-ray tube
a)Name the parts labelled A and B.
b)Explain how electrons are produced.
c)During the operation of the tube, the target becomes very hot.
i)Explain how this heat is caused.
ii)State any two ways in which cooling can be achieved.
d)Explain why:
i)The tube is evacuated.
ii)The cathode is concave shaped.
Date posted: October 30, 2019. Answers (1)
- A transformer uses 240V a.c supply to deliver 9.0A at 80V to a heating coil. If 10% of the energy taken from the supply is...(Solved)
A transformer uses 240V a.c supply to deliver 9.0A at 80V to a heating coil. If 10% of the energy taken from the supply is lost in the transformer itself, determine the current in the primary winding.
Date posted: October 30, 2019. Answers (1)
- A fishing boat uses ultrasound of frequency 6.0×104Hz to detect fish directly below. Two echoes of the ultrasound are received, one after 0.09 seconds coming...(Solved)
A fishing boat uses ultrasound of frequency 6.0×104Hz to detect fish directly below. Two echoes of the ultrasound are received, one after 0.09 seconds coming from the shoal of fish and the other after 0.12 seconds coming from the sea bed. The sea bed is 84m below the ultrasound transceiver.
i) State two reasons why ultrasound is preferred.
ii) Calculate the speed of the ultrasound waves in water.
Date posted: October 30, 2019. Answers (1)
- The diagram below shows a set up that was used to demonstrate that, sound is a mechanical wave.
i) State the function of the vacuum pump.
ii)...(Solved)
The diagram below shows a set up that was used to demonstrate that, sound is a mechanical wave.
i) State the function of the vacuum pump.
ii) When the switch is closed, state and explain what happens as the air is continuously drawn from the bell jar.
iii)State two possible reasons why it is not possible to reduce the sound completely in this experiment.
Date posted: October 30, 2019. Answers (1)
- Sound is a mechanical longitudinal wave. Explain why sound is classified as;
i)A mechanical wave.
ii)A longitudinal wave.(Solved)
Sound is a mechanical longitudinal wave. Explain why sound is classified as;
i)A mechanical wave.
ii)A longitudinal wave.
Date posted: October 30, 2019. Answers (1)
- A lens forms an image that is four times the size of the object on the screen. The distance between the object and the screen...(Solved)
A lens forms an image that is four times the size of the object on the screen. The distance between the object and the screen is 120cm.
i)State the type of lens used.
ii)Calculate the focal length of the lens.
Date posted: October 30, 2019. Answers (1)
- The figure below shows some of electromagnetic waves in the electromagnetic spectrum.
Arrange them in order of increasing energy contents. (Solved)
The figure below shows some of electromagnetic waves in the electromagnetic spectrum.
Arrange them in order of increasing energy contents.
Date posted: October 30, 2019. Answers (1)
- Diffraction is not a common phenomenon in light. Explain why.(Solved)
Diffraction is not a common phenomenon in light. Explain why.
Date posted: October 30, 2019. Answers (1)
- With the help of a diagram(s) show the difference between half-wave rectification and full-wave rectification output.(Solved)
With the help of a diagram(s) show the difference between half-wave rectification and full-wave rectification output.
Date posted: October 30, 2019. Answers (1)
- The activity of a radioactive source is initially 450 counts per second. After 72 hours, it reduces to 100 counts per second. If the background...(Solved)
The activity of a radioactive source is initially 450 counts per second. After 72 hours, it reduces to 100 counts per second. If the background count per second is 50, determine the half-life of the substance.
Date posted: October 30, 2019. Answers (1)
- The figure below shows a ray of light incident on the surface of one plane mirror.
Sketch the path of the ray on the diagram after...(Solved)
The figure below shows a ray of light incident on the surface of one plane mirror.
Sketch the path of the ray on the diagram after striking mirror 2 indicating all the angles.
Date posted: October 30, 2019. Answers (1)
- A gas container of volume 1.5×10-5m3 contains an ideal gas at a temperature of 270C and pressure 1.0×105 pa. Determine the volume of the gas...(Solved)
A gas container of volume 1.5×10-5m3 contains an ideal gas at a temperature of 270C and pressure 1.0×105 pa. Determine the volume of the gas when cooled to 170C and its pressure raised to 1.5×105 pa.
Date posted: October 30, 2019. Answers (1)
- In an experiment to determine the specific latent heat of vaporization of water, steam at 1000C was passed into water contained in a well lagged...(Solved)
In an experiment to determine the specific latent heat of vaporization of water, steam at 1000C was passed into water contained in a well lagged copper calorimeter. The following measurements were made:
- Mass of calorimeter = 55g
- Initial mass of water = 75g
-Final mass of calorimeter + water + condensed steam = 133g
- Final temperature of the mixture = 300C.
Specific heat capacity of water = 4200J/Kg/K.
Specific heat capacity of copper = 390J/Kg/K.
Determine the:
i)Mass of condensed steam
ii)Heat gained by the calorimeter and water if the initial temperature of the calorimeter
+ water = 200C
iii)Given that L is the specific latent heat of vaporization of steam.
(I)Write an expression for the heat given out by steam.
(II)Determine the value of L.
Date posted: October 30, 2019. Answers (1)
- The figure below shows a simple machine being used to raise a load W by applying an effort E.
i)Name the machine.
ii)Show that the velocity...(Solved)
The figure below shows a simple machine being used to raise a load W by applying an effort E.
i)Name the machine.
ii)Show that the velocity ratio (V.R) of the machine is given by R/r
iii)Given that r =11cm and R = 99cm, determine the effort E required to raise a load of 2800N
if the efficiency of the machine is 95%.
Date posted: October 30, 2019. Answers (1)
- Figure below shows dots which were made by a ticker timer tape attached to a trolley.
If the frequency used was 50Hz, determine;
a)The velocities between AB...(Solved)
Figure below shows dots which were made by a ticker timer tape attached to a trolley.
If the frequency used was 50Hz, determine;
a)The velocities between AB and BC.
b)The deceleration of the trolley.
Date posted: October 30, 2019. Answers (1)
- Figure below shows a uniform metre rule balancing when a mass of 200g is hung at one end.
Determine the tension T in the string. (Solved)
Figure below shows a uniform metre rule balancing when a mass of 200g is hung at one end.
Determine the tension T in the string.
Date posted: October 30, 2019. Answers (1)
- A person of mass 70kg stands on a scale balance in a lift. At a particular instant the lift is moving downward uniformly at 2.8m/s2....(Solved)
A person of mass 70kg stands on a scale balance in a lift. At a particular instant the lift is moving downward uniformly at 2.8m/s2. Calculate the reading on the scale in Newtons.
Date posted: October 30, 2019. Answers (1)
- The figure below shows a displacement time graph.
Describe the motion of the body between points:
OA
AB(Solved)
The figure below shows a displacement time graph.
Describe the motion of the body between points:
OA
AB
Date posted: October 30, 2019. Answers (1)
- The figure below shows a measuring cylinder which contains water initially at a level A.
A spherical solid is immersed in the water and the level...(Solved)
The figure below shows a measuring cylinder which contains water initially at a level A.
A spherical solid is immersed in the water and the level rises to B.
Determine the diameter of the spherical ball.
Date posted: October 30, 2019. Answers (1)
- Explain why a porridge in a cup wrapped with a wet cloth cools faster than when the cup is dipped in cold water.(Solved)
Explain why a porridge in a cup wrapped with a wet cloth cools faster than when the cup is dipped in cold water.
Date posted: October 28, 2019. Answers (1)