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- The maximum wavelength of light required to cause photoelectric emission on a metal surface is 8.0×10-7. The metal surface is irradiated with light of freque4ncy...(Solved)
The maximum wavelength of light required to cause photoelectric emission on a metal surface is 8.0×10-7. The metal surface is irradiated with light of freque4ncy 8.5 × 1014 Hz. Determine
i) The threshold frequency.
ii) The work function of the metal in electron volts.
iii) The maximum kinetic energy of the electron.
iv The maximum velocity of the emitted electrons.
(Take 1ev = 1.6×10-19J, C=3.0×108m/s, h=6.63×10-34Js and mass of electron = 9.11 × 10-31kg)
Date posted: May 27, 2019. Answers (1)
- An electric iron of resistance 60 and an indicator of resistance 500 are connected in parallel to a 240V mains supply.
Find the power dissipated.(Solved)
An electric iron of resistance 60 and an indicator of resistance 500 are connected in parallel to a 240V mains supply.
Find the power dissipated.
Date posted: May 27, 2019. Answers (1)
- The following diagram represents a reverse bias characteristics of p-n junction.
i) Draw a circuit diagram of a reverse biased p-n junction.
ii) From the graph, some...(Solved)
The following diagram represents a reverse bias characteristics of p-n junction.
i) Draw a circuit diagram of a reverse biased p-n junction.
ii) From the graph, some small amount of current flow in the circuit when voltage is zero. Explain.
iii) Current surge is noted at point P in the graph. Explain the cause of this surge.
Date posted: May 27, 2019. Answers (1)
- The following graph shows the potential difference, V against current, I for a certain device.
i) State with a reason whether the device obeys Ohm's law.
ii)...(Solved)
The following graph shows the potential difference, V against current, I for a certain device.
i) State with a reason whether the device obeys Ohm's law.
ii) Determine the resistance of the device when current is 1.5A.
iii) State how resistance of the device varies as current increases from zero to 5.0A.
Date posted: May 27, 2019. Answers (1)
- In a certain x-ray tube, the electrons are accelerated by a p.d. of 120,000V. Assuming that only 0.5% of the electrons energy goes into production...(Solved)
In a certain x-ray tube, the electrons are accelerated by a p.d. of 120,000V. Assuming that only 0.5% of the electrons energy goes into production of x-rays, determine the frequency of x-rays produced. (Take e=1.6 × 10-19C) (C=3.0×108m/s) (h=6.63×10-34Js)
Date posted: May 27, 2019. Answers (1)
- Fig below shows an X-ray tube
i) Name the parts labelled A and B.
ii) Explain how change in p.d. across P and Q changes the intensity...(Solved)
Fig below shows an X-ray tube
i) Name the parts labelled A and B.
ii) Explain how change in p.d. across P and Q changes the intensity of x-rays produced.
iii) What property of lead makes it suitable for use as shielding material.
Date posted: May 27, 2019. Answers (1)
- Fig below shows the deflection of a spot by an alternating voltage signal.
If sensitivity of the Y-gain is 30V/division, find the voltage of the signal.(Solved)
Fig below shows the deflection of a spot by an alternating voltage signal.
If sensitivity of the Y-gain is 30V/division, find the voltage of the signal.
Date posted: May 27, 2019. Answers (1)
- A transformer has 8000 turns in its primary coil and 200 turns in its secondary coil. The voltage in the primary coil is 240V.
Calculate voltage...(Solved)
A transformer has 8000 turns in its primary coil and 200 turns in its secondary coil. The voltage in the primary coil is 240V.
Calculate voltage in the secondary coil.
Date posted: May 27, 2019. Answers (1)
- The diagram below shows a magnetic material being magnetised.
Sketch a graph of magnetic strength against number of strokes for the material being magnetised on the...(Solved)
The diagram below shows a magnetic material being magnetised.
Sketch a graph of magnetic strength against number of strokes for the material being magnetised on the grid below.
Date posted: May 27, 2019. Answers (1)
- Explain how an electrostatic precipitator works.(Solved)
Explain how an electrostatic precipitator works.
Date posted: May 27, 2019. Answers (1)
- A ray of light is incident on a plane mirror as shown in figure below.
If the mirror is rotated anticlockwise through an angle of 20°,...(Solved)
A ray of light is incident on a plane mirror as shown in figure below.
If the mirror is rotated anticlockwise through an angle of 20°, what will be the angel of reflection.
Date posted: May 27, 2019. Answers (1)
- A pendulum bob takes 0.5 second to move from its mean position to a maximum displacement position. Calculate its frequency.(Solved)
A pendulum bob takes 0.5 second to move from its mean position to a maximum displacement position. Calculate its frequency.
Date posted: May 27, 2019. Answers (1)
- Calculate the angle of refraction for a ray of light incident to an air-glass interface, making an angle of a 50° with the interface.(Solved)
Calculate the angle of refraction for a ray of light incident to an air-glass interface, making an angle of a 50° with the interface.
Date posted: May 27, 2019. Answers (1)
- In an experiment to determine the power of an electric heater, melting ice was placed in a container with an outlet and the
heater placed in...(Solved)
In an experiment to determine the power of an electric heater, melting ice was placed in a container with an outlet and the heater placed in the ice as shown in the figure below.
i) Other than the current and voltage state two measurements that would be taken to determine the heat absorbed by the melted ice in a unit time.
ii) If the latent heat of fusion of ice is Lf show how measurements in (i) above would be used to determine the power (p) of the heater.
b) A can together with a stirrer of total heat capacity of 60J/k contains 200g of water at 10°C, dry steam at 100°C is passed
in while the water is stirred until the whole reaches a temperature of 30°C. Calculate the mass of the steam.
Date posted: May 27, 2019. Answers (1)
- A gun is fixed upwards from the top of an open truck moving horizontally at a uniform velocity of 50m/s, the bullet achieved a maximum...(Solved)
A gun is fixed upwards from the top of an open truck moving horizontally at a uniform velocity of 50m/s, the bullet achieved a maximum height of 45 m.
i) State with reason whether or not the bullet will land on the truck.
ii) Calculate the distance covered by the truck just before the bullet reached the same level from which it was fired.
Date posted: May 27, 2019. Answers (1)
- A simple hydrometer is made using a flat base test tube of mass 15g and length 12cm. The test tube is partly filled with lead...(Solved)
A simple hydrometer is made using a flat base test tube of mass 15g and length 12cm. The test tube is partly filled with lead shots. Given that the test tube has a uniform cross section are of 2.0cm² and 10cm of its length is under water. Calculate
i) The mass of the lead shots in the test tube.
ii) The length of the test tube immersed if placed in brine which has a density of 1.25g/cm³
iii) The lowest density of liquid in which this test tube would float.
Date posted: May 27, 2019. Answers (1)
- The diagram below shows a wooden block of dimensions 50cm by 40cm by 20cm held in a position by a string attached to the bottom...(Solved)
The diagram below shows a wooden block of dimensions 50cm by 40cm by 20cm held in a position by a string attached to the bottom of a swimming pool.
i) The three forces acting on the block are the tension (T) in the string, the weight (W) of the block and the upthrust (U) due to water.
Write an equation relating T, W and U when the block is at stationary.
ii) What is the weight of the block.
iii) What is the weight of the water displaced by the block.
iv) Determine the tension (T) on the string. (density of the block is 600kgm-3; density of water is 1000kgm-3)
Date posted: May 27, 2019. Answers (1)
- An astronaut climbing a very high mountain is likely to experience nose bleeding. Explain why this may happen(Solved)
An astronaut climbing a very high mountain is likely to experience nose bleeding. Explain why this may happen
Date posted: May 27, 2019. Answers (1)
- A model car moves round a circular track of radius 0.4m at 2 revolutions per second. Determine the linear velocity of the car.(Solved)
A model car moves round a circular track of radius 0.4m at 2 revolutions per second. Determine the linear velocity of the car.
Date posted: May 27, 2019. Answers (1)
- A gas of volume 84cm³ is compressed gradually at a constant temperature until its pressure rises from 75cmHg to 140cmHg.
Find the final volume of the...(Solved)
A gas of volume 84cm³ is compressed gradually at a constant temperature until its pressure rises from 75cmHg to 140cmHg.
Find the final volume of the gas.
Date posted: May 27, 2019. Answers (1)