Power supplies

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1. The voltage at the input to IC1 will be approximately: a) 6 V b) 12 V c) 13.5 V d) 16 V.

2. In the diagram for Question 1, the function of IC1 is: a) a current amplifier b) a voltage amplifier c) a voltage regulator d) a miniature transformer.

3. In the diagram for Question 1, the function of C19 is: a) a timing capacitor b) a coupling capacitor c) a reservoir capacitor d) waveshaping capacitor.

4. Which one of the following gives the frequency of the ripple produced by a full-wave bridge rectifier when fed from a 50Hz a.c. supply? a) 25 Hz b) 50 Hz c) 100 Hz d) 200 Hz.

5. When a power supply is tested, the output voltage falls from 12V on no-load to 10 V when the load current is 1 A. Which one of the following gives the output resistance of the power supply? a) 0.5 ohm b) 1 ohm c) 2 ohm d) 10 ohm.

6. Which one of the following is TRUE of the circuit shown below? a) The circuit acts as a voltage doubler b) The circuit acts as a voltage regulato c) The circuit acts as a bi-phase rectifier d) The circuit acts as a half-wave rectfifier.

7. The output voltage of a d.c. power supply falls from 20 V to 19 V when the a.c. mains supply voltage is reduced from 220 V to 200 V, Which one of the following gives the regulation of the supply? a) 0.5 % b) 1 % c) 2.5 % d) 5 %.

8. The output voltage of a switched mode power supply can be regulated by controlling the: a) duty cycle b) input voltage c) output current d) switching frequency.

9. Most switched mode power supplies operate in the frequency range: a) below 3 kHz b) 3 kHz to 10 kHz c) 10 kHz to 30 kHz d) above 30 kHz.

10. The advantages of a switched-mode power supply when compared with a conventional linear power supply include: a) low efficiency and compact size b) high efficiency and compact size c) low noise generation and high efficiency d) high noise generation and low efficiency.