Smk raja perempuan, ipoh latihan semasa cuti 2008 tingkatan 5 guided essay electronics spm 2007, paper 2 /Section B

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SPM 2007, PAPER 2 /Section B
Diagram 10.1 and Diagram 10.2 show two electrical circuits containing semiconductor diodes.

(a) What is meant by a semiconductor ? [1 mark]
(b) Using diagram 10.1 and Diagram 10.2, relate the lighting of the bulbs, the current and

the way the diode is connected to the terminals of the battery to deduce a relevant

physics concept. [5 mark]

(c) Diagram 10.3 shows a full wave rectifier circuit.

(i) Draw the wave form of a full wave rectification. [1 mark]

  1. A capacitor is placed across the output to smooth the current.

Draw the wave form produced.

Explain how a capacitors is used to smooth the current. [3 mark]

  1. Diagram 10.4 shows a circuit a transistor that acts as an automatic switch.

The transistor in the circuit causes the light emitting diode (LED) to light up

when it is dark.

A technician wants a fan labeled 240V, 100W in a room to be automatically switched on when the room is hot.

Suggest modifications that can be made to the circuit in Diagram 10.4 so that the fan

can be automatically switched on when the room is hot.

Draw the modified circuit.
State and explain the modifications based on the following aspects :
- the electrical components that are needed to replace the LED and the light dependent resistor (LDR) in the circuit.
- the positions of the electrical components in the circuit.

[10 mark]


(a) A conductivity between a conductor and insulator.

(b) Bulb in Diagram 10.1 not light but bulb in diagram 10.2 light up.

No current flow in the circuit in diagram 10.1 but current flow in circuit in diagram 10.2.

In diagram 10.1, positive terminal is connected to the n junction but in diagram 10.2 positive terminal is connected to the p junction.

c) i)

Relay at collector circuit as switch the second circuit.

Thermistor to detect heat. When heat increase resistor of thermistor become decrease.

When VThemistor is low VBase is high.

Ib and Ic is flow.

Relay at secondary circuit is switch on the fan.

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