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(i) The heart from the filament heats up cathode, causing the electrons to be dislodged from the surface.
(ii) The grid controls the intensity of electron beam reaching the screen, hence brightness. It is negatively charged to repel the electrons hence increasing or decreasing the number reaching the screen.
(iii) A vertical line would appear.
johnmulu answered the question on June 5, 2017 at 13:09
- Figure 12 shows a section of a house wiring system. (Solved)
Figure 12 shows a section of a house wiring system.
(i) Name:
the circuit labeled P.
the terminals labeled X and Y.
(ii) I. State the purpose of R in the circuit.
II. Give a reason why R is connected to Y but not to X.
(iii) Why is the earthing necessary in such a circuit?
Date posted: June 5, 2017. Answers (1)
- Figure 17 shows the electric wiring of an electric heater. A, B, C are the mains wires. (Solved)
Figure 17 shows the electric wiring of an electric heater. A, B, C are the mains wires.
Identify A, B and C.
Date posted: June 5, 2017. Answers (1)
- Figure 4 shows a simple transformer connected to a 12 V a.c source and an a.c voltmeter. (Solved)
Figure 4 shows a simple transformer connected to a 12 V a.c source and an a.c voltmeter.
By counting the number of turns in each coil, determine the reading on the voltmeter.
Date posted: June 5, 2017. Answers (1)
- Figure 15, shows two coils A and B placed close to each other. A is connected to a steady D.C. Supply and a switch, B is connected to a sensitive galvanometer. (Solved)
Figure 15, shows two coils A and B placed close to each other. A is connected to a steady D.C. Supply and a switch, B is connected to a sensitive galvanometer.
(i) The switch is now closed. State the observations made on the galvanometer.
(ii) Explain what would be observed if the switch is then open.
Date posted: June 5, 2017. Answers (1)
- Figure 6 shows a horizontal conductor in a magnetic field parallel to the plane of the paper. (Solved)
Figure 6 shows a horizontal conductor in a magnetic field parallel to the plane of the paper.
State the direction in which the wire may be moved so that the induced current is in the direction shown by the arrow.
Date posted: June 5, 2017. Answers (1)
- Figure 5 shows a magnet being moved towards a stationary solenoid. It is observed that a current flows through the circuit in a direction Q to P. (Solved)
Figure 5 shows a magnet being moved towards a stationary solenoid. It is observed that a current flows through the circuit in a direction Q to P.
Explain: (i) How the current is produced
(ii) Why the current flows from Q to P.
Date posted: June 5, 2017. Answers (1)
- Figure 12 shows two circuits close to each other. (Solved)
Figure 12 shows two circuits close to each other.
When the switch is closed, the galvanometer shows a reading and then returns to zero. When the switch is then opened, the galvanometer shows a reading in the opposite direction and then returns to zero. Explain these observations.
Date posted: June 5, 2017. Answers (1)
- Figure 13 shows a simple microphone in which sound waves from the person talking cause the cardboard diaphragm to vibrate. (Solved)
Figure 13 shows a simple microphone in which sound waves from the person talking cause the cardboard diaphragm to vibrate.
(i) Explain how a varying current is induced in the coil when the diaphragm vibrates
(ii) State two ways in which the induced current in (i) above can be increased.
Date posted: June 5, 2017. Answers (1)
- Figure 10 shows a simple electric generator. (Solved)
Figure 10 shows a simple electric generator.
Name the parts labeled P and Q
Date posted: June 5, 2017. Answers (1)
- In the set up in Figure 19, the magnet is moved towards the coil and stopped when inside the coil. (Solved)
In the set up in Figure 19, the magnet is moved towards the coil and stopped when inside the coil.
It is observed that the galvanometer deflects to one side and then goes back to zero. Explain this observation.
Date posted: June 5, 2017. Answers (1)
- Figure 7 shows pendulum A and pendulum B freely suspended between the poles of identical magnets. Pendulum A is made of thick copper plate while B is made a copper plate with slots. (Solved)
Figure 7 shows pendulum A and pendulum B freely suspended between the poles of identical magnets. Pendulum A is made of thick copper plate while B is made a copper plate with slots.
When the two are set to swing, it is observed that A slows down faster than B Explain this observation.
Date posted: June 5, 2017. Answers (1)
- Two identical copper coils P and Q are placed close to each other as shown in Figure 17. Coil P is connected to a D.C power supply and coil Q is connected to a galvanometer, G. Use this information to answer questions (a) and (b). (Solved)
Two identical copper coils P and Q are placed close to each other as shown in Figure 17. Coil P is connected to a D.C power supply and coil Q is connected to a galvanometer, G. Use this information to answer questions (a) and (b).
(a) State and explain what would be observed on the galvanometer immediately the switch S is closed.
(b) State with reason the difference that would be noted in the observation made in question (a) if the number of turns in coils Q were doubled.
Date posted: June 5, 2017. Answers (1)
- Figure 15 shows a wire XY placed in a magnetic field. (Solved)
Figure 15 shows a wire XY placed in a magnetic field.
State the direction in which the wire must be moved for the current to move in the direction shown
Date posted: June 5, 2017. Answers (1)
- Figure 6 represents a step-down transformer with 500 turns in the primary and 50 turns in the secondary. The turns are wound uniformly on the core. The lengths of PQ and QR are indicated. (Solved)
Figure 6 represents a step-down transformer with 500 turns in the primary and 50 turns in the secondary. The turns are wound uniformly on the core. The lengths of PQ and QR are indicated.
Determine the p.d across PQ.
Date posted: June 5, 2017. Answers (1)
- Table 1 shows radiations and their respective frequencies. (Solved)
Table 1 shows radiations and their respective frequencies.
Arrange the radiations in the order of increasing energy.
Date posted: June 5, 2017. Answers (1)
- The chart below shows an arrangement of different parts of the electromagnetic spectrum. (Solved)
The chart below shows an arrangement of different parts of the electromagnetic spectrum.
Name the radiation represented by A.
Date posted: June 5, 2017. Answers (1)
- Table 1 carries information on the type of radiation, detector and use for some of the electromagnetic radiations. Fill in the blanks. (Solved)
Table 1 carries information on the type of radiation, detector and use for some of the electromagnetic radiations. Fill in the blanks.
Date posted: June 5, 2017. Answers (1)
- Figure 11 shows a test-tube whose cross-sectional area is 2 cm2 partially filled with lead shot floating vertically in water. (Solved)
Figure 11 shows a test-tube whose cross-sectional area is 2 cm2 partially filled with lead shot floating vertically in water.
(i) Determine the: volume of the water displaced;
(ii) Determine weight of water displaced.
(iii) State the combined weight of the test-tube and the lead shot.
Date posted: June 5, 2017. Answers (1)
- Figure 13 shows a hydrometer with a thin stem floating in water in a beaker. (Solved)
Figure 13 shows a hydrometer with a thin stem floating in water in a beaker.
State with a reason what is observed on the hydrometer when the temperature of the water is raised.
Date posted: June 5, 2017. Answers (1)
- Figure 13 shows a log of wood of mass 20 kg submerged in water in a pond and held in position by a string fixed to the bottom of the pond. (Solved)
Figure 13 shows a log of wood of mass 20 kg submerged in water in a pond and held in position by a string fixed to the bottom of the pond.
Given that the density of water is 1000 kgm -3 and that of wood is 800 kgm -3, determine the;
(i) volume of the log
(ii) Upthrust of the log
(iii) Tension in the string.
Date posted: June 5, 2017. Answers (1)