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U.V light dislodges electrons from zinc plate.Electrons are repelled by the negatively charged electroscope.This lowers the excess charge on leaf leading to collapse.In figure (b) UV light dislodges electrons from zinc plate positively charged electroscope will re-attract the electrons are kept keeps the charge constant.
sharon kalunda answered the question on May 31, 2019 at 08:52
- The diagram below shows a micrometer screw gauge used by a student to measure the thickness of a wire. If it has a zero error...(Solved)
The diagram below shows a micrometer screw gauge used by a student to measure the thickness of a wire. If it has a zero error of 0.06mm, what is the actual thickness of the wire?
Date posted: May 31, 2019. Answers (1)
- State two advantages of the use of alternating voltage for the transmission of electrical energy.(Solved)
State two advantages of the use of alternating voltage for the transmission of electrical energy.
Date posted: May 31, 2019. Answers (1)
- A transformer is used to provide a potential difference of 100KV to an X-ray tube from 250V a.c mains supply. A current of 100mA flows...(Solved)
A transformer is used to provide a potential difference of 100KV to an X-ray tube from 250V a.c mains supply. A current of 100mA flows in ht X-ray tube and the transformer is 100% efficient. Calculate:-
(i) The ratio of the number of turns of the secondary coil to the number of turns in the primary coil.
(ii) The current in the primary coil.
(iii) State giving reasons which of the coils of the transformer is thinner.
Date posted: May 31, 2019. Answers (1)
- State one difference and one similarity between a step up transformer and an induction coil.(Solved)
State one difference and one similarity between a step up transformer and an induction coil.
Date posted: May 31, 2019. Answers (1)
- The figure below shows a simple transformer. Study it and answer the questions that follow.
i) Explain why the core is a continuous loop.
ii) Give...(Solved)
The figure below shows a simple transformer. Study it and answer the questions that follow.
i) Explain why the core is a continuous loop.
ii) Give a reason as to why the core is laminated.
iii) State and explain which coils are thicker.
Date posted: May 31, 2019. Answers (1)
- The figure below shows a ray of light incidents on glass-air interface.
Given that the refractive index of glass is 1.48, determine the value of theta.(Solved)
The figure below shows a ray of light incidents on glass-air interface.
Given that the refractive index of glass is 1.48, determine the value of theta.
Date posted: May 31, 2019. Answers (1)
- In the figure below the bar magnet is moved into the coil.
(i) State and explain what is observed in the galvanometer.
(ii) Explain briefly the...(Solved)
In the figure below the bar magnet is moved into the coil.
(i) State and explain what is observed in the galvanometer.
(ii) Explain briefly the source of an electrical energy in the circuit.
Date posted: May 31, 2019. Answers (1)
- In an experiment to determine the refractive index of a liquid, the liquid was poured into a measuring cylinder, a pin was
placed at the bottom...(Solved)
In an experiment to determine the refractive index of a liquid, the liquid was poured into a measuring cylinder, a pin was
placed at the bottom of the cylinder and another pin was used to locate the apparent position of the first pin. The values
of real and apparent depth were used to plot a graph in the figure below.
i) From the graph determine the refractive index of the liquid.
ii) Given that the velocity of light in vacuum is 3.0 x 108 m/s what would be the velocity of light in the liquid
above.
Date posted: May 31, 2019. Answers (1)
- The figure below shows an object O placed in front of an objective lens Lo whose focal length fo is less than fe, the focal...(Solved)
The figure below shows an object O placed in front of an objective lens Lo whose focal length fo is less than fe, the focal length of the eyepiece Le. Complete using ray construction how the arrangement would produce a compound microscope.
Date posted: May 31, 2019. Answers (1)
- The initial mass of a radioactive substance is 20g. The substance has a half -life of 5 years. Determine the mass remaining after 20 years.(Solved)
The initial mass of a radioactive substance is 20g. The substance has a half -life of 5 years. Determine the mass remaining after 20 years.
Date posted: May 31, 2019. Answers (1)
- The diagram below shows an arrangement of capacitors in a circuit.
Determine:-
(i) The total capacitance
(ii) The total charge
(iii) The energy stored by the 2µF...(Solved)
The diagram below shows an arrangement of capacitors in a circuit.
Determine:-
(i) The total capacitance
(ii) The total charge
(iii) The energy stored by the 2μF capacitor.
Date posted: May 31, 2019. Answers (1)
- Explain why carbon -14 is radioactive while Carbon -12 is not.(Solved)
Explain why carbon -14 is radioactive while Carbon -12 is not.
Date posted: May 31, 2019. Answers (1)
- The cell in the figure below has an e.m.f. of 1.8V and negligible internal resistance.
Determine:-
(i) Total resistance in the circuit.
(ii) The current in the...(Solved)
The cell in the figure below has an e.m.f. of 1.8V and negligible internal resistance.
Determine:-
(i) Total resistance in the circuit.
(ii) The current in the circuit.
(iii) Reading of the voltmeter.
Date posted: May 31, 2019. Answers (1)
- The figure below shows an object O infront of a concave mirror and its image, I, formed after reflection.
On the same diagram draw appropriate ray(s)...(Solved)
The figure below shows an object O infront of a concave mirror and its image, I, formed after reflection.
On the same diagram draw appropriate ray(s) to locate the principal focus F, of the mirror.
Date posted: May 31, 2019. Answers (1)
- The figure below shows a ray of light incident in the face of a water prism.
Sketch the path of the ray of light as it...(Solved)
The figure below shows a ray of light incident in the face of a water prism.
Sketch the path of the ray of light as it passes through the prism. Critical angle for water is 49°.
Date posted: May 31, 2019. Answers (1)
- In figure shown below (not drawn to scale), sketch the path of a ray till it emerges from the prism.(Solved)
In figure shown below (not drawn to scale), sketch the path of a ray till it emerges from the prism.
Date posted: May 31, 2019. Answers (1)
- The figure below shows a series of wave fronts one wavelength apart approaching a gap between barriers in ripple tank.
On the same diagram, show what...(Solved)
The figure below shows a series of wave fronts one wavelength apart approaching a gap between barriers in ripple tank.
On the same diagram, show what happens when the waves pass through the gap.
Date posted: May 31, 2019. Answers (1)
- The figure below shows wave fronts approaching a concave sphere.
Complete the diagram to show wave fronts formed after striking the surface. Show how focal point...(Solved)
The figure below shows wave fronts approaching a concave sphere.
Complete the diagram to show wave fronts formed after striking the surface. Show how focal point of the surface is located.
Date posted: May 31, 2019. Answers (1)
- The figure below shows a displacement time graph for a wave motion.
What is the frequency of the wave?(Solved)
The figure below shows a displacement time graph for a wave motion.
What is the frequency of the wave?
Date posted: May 31, 2019. Answers (1)
- The figure below shows a diagram of a current -carrying wire wound on a U-shaped soft iron.
Draw the magnetic field pattern around P and Q.(Solved)
The figure below shows a diagram of a current -carrying wire wound on a U-shaped soft iron.
Draw the magnetic field pattern around P and Q.
Date posted: May 31, 2019. Answers (1)