When excess current flows through the circuit, increased magnetic power makes the soft iron core to attract the soft iron
armature thus opening the switch current flow.
sharon kalunda answered the question on May 29, 2019 at 12:21
- One method of making a simple d.c motor more powerful is to wind the coil on a soft iron core. Explain how this
method increases the...(Solved)
One method of making a simple d.c motor more powerful is to wind the coil on a soft iron core. Explain how this
method increases the power of the motor.
Date posted: May 29, 2019. Answers (1)
- A student while investigating the focal length of a certain concave mirror, measured object and image distances
and drew a graph of 1/u against 1/v shown...(Solved)
A student while investigating the focal length of a certain concave mirror, measured object and image distances
and drew a graph of 1/u against 1/v shown below.
From the graph, determine the focal length.
Date posted: May 29, 2019. Answers (1)
- The figure below shows an object O placed infront of a concave mirror.
a) Draw rays of light from the object to the mirror to show...(Solved)
The figure below shows an object O placed infront of a concave mirror.
a) Draw rays of light from the object to the mirror to show how the image is formed.
b) State one
i) similarity between the image formed in (a) above and that formed by a plane mirror.
ii) application of the set up in (a) above.
Date posted: May 29, 2019. Answers (1)
- What is meant by the term “topping” as applied to a lead acid accumulator ?(Solved)
What is meant by the term “topping” as applied to a lead acid accumulator ?
Date posted: May 29, 2019. Answers (1)
- The figure below shows a gold leaf electroscope charged negatively.
State and explain what happens to the leaf when a negative charged rod is brought near...(Solved)
The figure below shows a gold leaf electroscope charged negatively.
State and explain what happens to the leaf when a negative charged rod is brought near the cap without touching it.
Date posted: May 29, 2019. Answers (1)
- The figure below shows a ray of light XY striking the mirror CD held at an angle of 1080 to mirror DE.Complete the path of...(Solved)
The figure below shows a ray of light XY striking the mirror CD held at an angle of 1080 to mirror DE.
Complete the path of the ray XY and state the final angle of reflection.
Date posted: May 29, 2019. Answers (1)
- 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)