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When the switch is closed, the magnetic field builds up to maximum is primary coil inducing a current in secondary coil. When the current is maximum there is no change in magnetic flux. When the switch is open, the magnetic field flux decreases to zero, carrying current to be induced in the secondary coil but in the opposite direction.
johnmulu answered the question on June 5, 2017 at 11:53
- 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)
- Figure 12 shows a weighing balance on which a beaker containing some water is placed. The reading on the balance is 2.80 N. A metal block weighing 2.7 N is suspended from a spring balance. (Solved)
Figure 12 shows a weighing balance on which a beaker containing some water is placed. The reading on the balance is 2.80 N. A metal block weighing 2.7 N is suspended from a spring balance.
(i) State what is observed on the spring balance and the weighing balance, as the metal block is gradually lowered into the water.
(I) Observation on spring balance.
(II) Observation on weighing balance
(ii) Explain the observation made on the spring balance in (I).
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)
- Figure 18 shows parts of a simple submarine, a ship that can travel both on water and under water. To do this water is pumped in or out of the ballast tanks. (Solved)
Figure 18 shows parts of a simple submarine, a ship that can travel both on water and under water. To do this water is pumped in or out of the ballast tanks.
Explain how the tanks are used to change the depth of the submarine.
Date posted: June 5, 2017. Answers (1)
- Figure 8 shows a stone of mass 4.0 kg increased in water and suspended from a spring balance(Solved)
Figure 8 shows a stone of mass 4.0 kg increased in water and suspended from a spring balance with a string. The beaker was placed on a compression balance whose reading was 85 N. The density of the stone was 3000 kgm-3 while the density of the liquid was 800 kgm -3.
Determine the;
(a) volume of the liquid displaced;
(b) upthrust on the stone;
(c) Reading of the spring balance;
Date posted: June 5, 2017. Answers (1)
- Figure 10 shows a rectangular metal block of density 10500 kgm-3(Solved)
Figure 10 shows a rectangular metal block of density 10500 kgm-3 and dimensions 30 cm x 20 cm x 20 cm suspended inside a liquid of density 1200 kgm-3 by a string attached to a point above the liquid. The three forces acting on the block are the tension T, On the string, the weight W, of the block and the upthrust, U due to the liquid.
(i) Write the expression relating T, W and U when the block is in equilibrium inside the liquid.
(ii) Determine the weight, W of the block.
(iii) Determine the weight of the liquid displaced by the fully submerged block.
(iv) Hence determine the tension, T in the string.
Date posted: June 5, 2017. Answers (1)
- The system in Figure below is in equilibrium. (Solved)
The system in Figure below is in equilibrium.
When temperature of the water is raised the system is observed to tilt to the right. State the reason for this observation.
Date posted: June 5, 2017. Answers (1)
- Figure 14 shows a cork floating on water and held to the bottom of the beaker by a thin thread. (Solved)
Figure 14 shows a cork floating on water and held to the bottom of the beaker by a thin thread.
(i) Name the forces acting on the cork
(ii) Describe how each of the forces mentioned in (i) above changes when water is added into the beaker until it fills up.
Date posted: June 5, 2017. Answers (1)