(i) To ensure that all the electrons emitted by the cathode reach the anode to maximize the photo current.
(ii) To limit control or lower the current in the circuit.
(iii) The energy of the incident light must be greater than work function of the cathode surface if photo electron emission has to occur.
(iv) The current flowing in the circuit ensures that the relay switch is attracted to the electromagnet.
When UV light is cut-off, the photo current ceases and the relay switch completes the burglar alarm circuit and the alarm sounds.
sharon kalunda answered the question on September 6, 2019 at 08:53
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The figure below illustrates a method of charging a metal sphere.
(Solved)
The figure below illustrates a method of charging a metal sphere.
(i) Name the method of charging shown in the figure.
(ii) Indicate the final charge on the sphere in the figure.
Date posted:
September 6, 2019
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Answers (1)
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In an experiment to investigate factors affecting capacitance of a capacitor, a student increased the area of the plates and decreased the separation of the...
(Solved)
In an experiment to investigate factors affecting capacitance of a capacitor, a student increased the area of the plates and decreased the separation of the plates. Explain the effect on the capacitance when
(i) the area of plates increased
(ii) the distance of the separation of the plates decreased
Date posted:
September 6, 2019
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Answers (1)
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A converging lens forms an image which is three times the object. Determine the focal length of the lens if the distance between the object...
(Solved)
A converging lens forms an image which is three times the object. Determine the focal length of the lens if the distance between the object and the screen is 80cm.
Date posted:
September 6, 2019
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Answers (1)
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The graph below shows the variation of 1/v and 1/u in an experiment to determine the focal length of a lens.
(Solved)
The graph below shows the variation of 1/v and 1/u in an experiment to determine the focal length of a lens.
(i) Use the graph to determine the focal length
(ii) What is the power of the lens used?
Date posted:
September 6, 2019
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Answers (1)
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An optician in Eldoret Hospital examined an eye of a patient and made the following observations:
Eye too short and the focal length of the eye...
(Solved)
An optician in Eldoret Hospital examined an eye of a patient and made the following observations:
Eye too short and the focal length of the eye lens short
(i) State the eye defect the patient could be having.
(ii) Use a diagram to describe how the defect could be corrected.
Date posted:
September 6, 2019
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Answers (1)
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Some students wish to determine the focal length of a convex lens of thickness 0.6cm using an optical pin and a plane mirror.The figure shows...
(Solved)
Some students wish to determine the focal length of a convex lens of thickness 0.6cm using an optical pin and a plane mirror.The figure shows the experimental set up when there is no parallax between the pin and the image.
Determine the focal length of the lens.
Date posted:
September 6, 2019
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Answers (1)
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Below is part of a circuit that was setup by form four students of Okok Seconday School during a physics practical lesson to demonstrate full...
(Solved)
Below is part of a circuit that was setup by form four students of Okok Seconday School during a physics practical lesson to demonstrate full wave rectification using two diodes. Complete the circuit by correctly placing the load R and two diodes.
Date posted:
September 6, 2019
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Answers (1)
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A sample of a radioactive substance initially has 8.0 x 1025 particles. The half life of the sample is 98 seconds. Determine the number of...
(Solved)
A sample of a radioactive substance initially has 8.0 x 1025 particles. The half life of the sample is 98 seconds. Determine the number of particles that will remain after 294 seconds.
Date posted:
September 6, 2019
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Answers (1)
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A form two student from Kimomo Secondary School found his dry cells leaking on removing from his torch. What would be the possible cause of...
(Solved)
A form two student from Kimomo Secondary School found his dry cells leaking on removing from his torch. What would be the possible cause of the leakage?
Date posted:
September 6, 2019
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Answers (1)
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A vibrator is sending out 8 ripples per second across a ripple water tank. The ripples are observed to be 4cm apart. Calculate the velocity...
(Solved)
A vibrator is sending out 8 ripples per second across a ripple water tank. The ripples are observed to be 4cm apart. Calculate the velocity of the ripples
Date posted:
September 6, 2019
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Answers (1)
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One of the factors that affect efficiency of a transformer is hysteresis losses. What is hyteresis losses?
(Solved)
One of the factors that affect efficiency of a transformer is hysteresis losses. What is hyteresis losses?
Date posted:
September 6, 2019
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Answers (1)
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Give a reason why x-rays but not radio waves are used to detect fractured bones.
(Solved)
Give a reason why x-rays but not radio waves are used to detect fractured bones.
Date posted:
September 6, 2019
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Answers (1)
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The following figure shows the path of a ray of light through a transparent material placed in air.
(Solved)
The following figure shows the path of a ray of light through a transparent material placed in air.
Determine the refractive index of the transparent material
Date posted:
September 6, 2019
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Answers (1)
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The control grid in a cathode ray oscilloscope (CRO) is used to control the brightness of the beam on the screen. Explain how the brightness...
(Solved)
The control grid in a cathode ray oscilloscope (CRO) is used to control the brightness of the beam on the screen. Explain how the brightness of the beam can be increased.
Date posted:
September 6, 2019
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Answers (1)
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A current of 0.7A flows through a wire when a potential difference of 0.35V is applied at the ends of the wire. If the wire...
(Solved)
A current of 0.7A flows through a wire when a potential difference of 0.35V is applied at the ends of the wire. If the wire is 0.5m long and has a cross-sectional area of 8.0 x 103mm2, determine its resistivity.
Date posted:
September 6, 2019
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Answers (1)
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The figure below shows a positively charged metal plate with an earthing connection. State and explain the final charge of the plate.
(Solved)
The figure below shows a positively charged metal plate with an earthing connection. State and explain the final charge of the plate.
Date posted:
September 6, 2019
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Answers (1)
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The figure below shows a load of 50N being raised by pulling it along an inclined plane of length 2.0m.
(Solved)
The figure below shows a load of 50N being raised by pulling it along an inclined plane of length 2.0m.
Determine
i. The work done by the 22N force
ii. The work done against the load
iii. The efficiency of the system
Date posted:
September 6, 2019
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Answers (1)
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The figure below shows a buoy of capacity 40 litres and mass 10kg. It is held in position in sea water of
density 1.04g/cm3 by a...
(Solved)
The figure below shows a buoy of capacity 40 litres and mass 10kg. It is held in position in sea water of
density 1.04g/cm3 by a light cable fixed to the bottom so that ¾ of its volume is below the water surface.
Determine the tension in the cable.
Date posted:
September 6, 2019
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Answers (1)
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The figure below shows a block with a graduated side and dimensions 4cm by 16cm, just about to be lowered
into a liquid in an overflow...
(Solved)
The figure below shows a block with a graduated side and dimensions 4cm by 16cm, just about to be lowered
into a liquid in an overflow can.
During an experiment with this set-up, the following was recorded:
- The block floated with three-quarter of it submerged.
- Initial reading of balance = 0g
- Final reading of balance = 154g
Use the information to determine the density of
(i) the block
(ii) the liquid
Date posted:
September 6, 2019
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Answers (1)
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A bicycle wheel makes 300 revolutions per minute. Calculate the angular velocity of the wheel.
(Solved)
A bicycle wheel makes 300 revolutions per minute. Calculate the angular velocity of the wheel.
Date posted:
September 6, 2019
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Answers (1)