GET THE KCSE PREDICTION ELECTRICITY (Theory)–P1 MARKING SCHEMES HERE

Bunyore

SECTION A (48 marks)

Answer all the questions in this section in the spaces provided

1. (a)        List four insulating materials used in electrical installations.                                    (2 marks)

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(b)        State two advantages of mineral insulated copper sheathed cables over PVC sheathed.                                                                                                                                                                  (2 marks)

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2. (a)        State Lenz’s law of electromagnetic induction.                                                         (2 marks)

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(b)        Name four applications of electromagnets.                                                                (2 marks)

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3. (a)        Name four National Polytechnics in Kenya.                                                             (2 marks)

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(b)        List two business opportunities in the field of electricity.                                          (1 mark)

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4. (a)        State how each of the following electrical material waste should be disposed safely:
5. Burnt fluorescent tubes;                                                                                  (½ mark)

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• Damaged computers.                                                                                      (½ mark)

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(b)        State the application of each of the following types of extinguishers:

• Carbon dioxide;                                                                                              (1 mark)

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• Water.                                                                                                             (1 mark)

……………………………………………………………………………………………………………………………………………………………………………………………………………………………… (a)        Figure 1 shows a carbon resistor with color codes. Determine the value of the resistor given,                                                                                                                                                        (2 marks

Figure 2 shows a resistive circuit.

Determine the:

• Value of the resistor B if the total circuit resistance is 20Ω;                                      (4 marks)

• Total circuit current.                                                                                                   (2 marks)

1. (a)        Name four parts of a fluorescent fitting.                                                                    (2 marks)

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• List four marking out tools used in fabricating sheet metal casing.                           (2 marks)

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2. (a)        Figure 3 shows two views of an object drawn in third angle projection.

On the grid provided, make a free hand isometric sketch with corner N as the lowest point.                                                                                                                                                   (3marks)

(b)        Outline two ways that can be used to troubleshoot a faulty television.                     (2 marks)

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1. (a)        With the aid of sketches, distinguish between P-N-P and an N-P-N transistor.        (3 marks)

(b)        Name four applications of a P-N junction diode.                                                     (2 marks)

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2. (a)        State three advantages of digital instruments over analogue instruments.                 (3 marks)

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(b)        An ideal transformer connected to a 240V mains supplies a 12V, 120W lamp. Calculate the:

• Transformer’s turns ratio;                                                                               (3 marks)

• Current taken from the supply.                                                                       (3 marks)

SECTION B (52 marks) GET THE KCSE PREDICTION ELECTRICITY (Theory)–P1 MARKING SCHEMES HERE

Answer any four questions in the spaces provided.

3. (a)        (i)         Convert 23₁₀ to binary.                                                                                   (2 marks)

(ii)        Convert 11011₂ to decimal.                                                                            (2 marks)

(b)        Draw a truth table for each of the following logic gate;

            (i)         NOR;                                                                                                              (4 marks)

            (ii)        NAND.                                                                                                           (4 marks)

(c)        Name two applications of logic gates.                                                                        (1 mark)

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4. (a)        Draw a sine wave and indicate the following:                                   
5. Peak value;                                                                                                      (5 marks)
6. Instantaneous value;
7. Cycle.

(b) Figure 4 shows an RLC circuit.

Calculate the:

• Inductive reactance;                                                                                                    (2 marks)

• Capacitive reactance;                                                                                                  (2 marks)

• Circuit impedance;                                                                                                      (2 marks)

• Circuit current.                                                                                                            (2 marks)

1. (a)        State;
2. Two advantages of a moving coil instrument.                                               (2 marks)

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• Two essential features of an analogue instrument.                                         (2 marks)

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(b)        With the aid of a labelled diagram, explain the Flemmings right hand rule to demonstrate the                        direction of induced EMF.                                                                                          (6 marks)

(c)        show that for two capacitors C₁ and C₂ connected in series, the total capacitance is given by:

(3 marks)

• (a)        State:
• Two advantages of trunking over steel conduit wiring systems.                   (2 marks)

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• Two advantages of MCBs over rewirable fuses.                                            (2 marks)

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(b)        (i)         Draw and label a diagram of a switch start fluorescent fitting.                     (6 marks)

(ii)       Outline three tests carried out in a completed electrical installation.            (3 marks)

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Figure 5 shows a machine block drawing of an isometric projection

Draw the following views in full size in first angle projection:

• Front elevation in the direction of arrow F:
• Plan;
• Indicate six dimensions.                                                                                              (13 marks)