Power Supplies, Batteries, Transformers,
Rectifiers, Filters, Regulator
Basic Qualification Question Bank for Amateur Radio Operator Certificate Examinations 12 June, 2014

Power Supplies

(A)

B-003-017-001 If your mobile transceiver works in your car but not in your home, what should you check first?
A The power supply
B The speaker
C The microphone
D The SWR meter

(B) What device converts household current to 12 volts DC?
A A catalytic converter
B A power supply
C A low pass filter
D An RS-232 interface

(B)
B-003-017-003 Which of these usually needs a high current capacity power supply?
A An SWR meter
B A transceiver
C An antenna switch

(B)
B-003-017-008 Power-line voltages have been made standard over the years and the voltages generally supplied to homes are approximately:
A 130 and 260 volts
B 120 and 240 volts
C 110 and 220 volts
D 100 and 200 volts

(C)
B-003-017-009 Your mobile HF transceiver draws 22 amperes on transmit. The manufacturer suggests limiting voltage drop to 0.5 volt and the vehicle battery is 3 metres(10 feet) away. Given the losses below at that current, which minimum wire gauge must you use?
A Number 10, 0.07 V per metre(0.02 V per foot)
B Number 8, 0.05 V per metre(0.01 V per foot)
C Number 12, 0.11 V per metre(0.03 V per foot)
D Number 14, 0.19 V per metre(0.06 V per foot)

(A)
B-003-017-010 Why are fuses needed as close as possible to the vehicle battery when wiring a transceiver directly to the battery?
A To prevent an overcurrent situation from starting a fire
B To prevent interference to the vehicle's electronic systems
C To reduce the voltage drop in the radio's DC supply
D To protect the radio from transient voltages

Batteries

(A)

B-003-016-001 How much voltage does a standard automobile battery usually supply?

(B)
B-003-016-002 Which component has a positive and a negative side?
A A resistor
B A battery
C A potentiometer
D A fuse

(C)
B-003-016-003 A cell, that can be repeatedly recharged by supplying it with electrical energy, is known as a:
A memory cell
B primary cell
C storage cell
D low leakage cell

(B) Which of the following is a source of electromotive force(EMF)?
A carbon resistor
B lithium-ion battery
C germanium diode
D P channel FET

(C)
B-003-016-005 An important difference between a conventional flashlight battery and a lead acid battery is that only the lead acid battery:
A can be completely discharged
B contains an electrolyte
C can be repeatedly recharged
D has two terminals

(A)
B-003-016-006 An alkaline cell has a nominal voltage of 1.5 volts. When supplying a great deal of current, the voltage may drop to 1.2 volts. This is caused by the cell's:
A internal resistance
B electrolyte becoming dry
C current capacity
D voltage capacity

(C)
B-003-016-007 An inexpensive primary cell in use today is the carbon-zinc or flashlight cell. This type of cell can be recharged:
A many times
B once
C never
D twice

(A)
B-003-016-008 Battery capacity is commonly stated as a value of current delivered over a specified period of time. What is the effect of exceeding that specified current?
A A battery charge will not last as long
B The internal resistance of the cell is short-circuited
C The battery will accept the subsequent charge in shorter time
D The voltage delivered will be higher

(A)
B-003-016-009 To increase the current capacity of a cell, several cells should be connected in:
A parallel
B series
C parallel resonant
D series resonant

(A)
B-003-016-010 To increase the voltage output, several cells are connected in:
A series
B parallel
C series-parallel
D resonance

(D)
B-003-016-011 A lithium-ion battery should never be:
A recharged
B left disconnected
C left overnight at room temperature
D short-circuited

Transformer

(D)

B-003-008-001 In a regulated power supply, the transformer connects to an external source which is referred to as______________.
A regulator
B filter
C rectifier
D input

(C)
B-003-008-002 In a regulated power supply, the _______________ is between the input and the rectifier.
A regulator
B filter
C transformer
D output

(A)
B-003-008-006 In a regulated power supply, the _______________is connected to the regulator.
A output
B rectifier
C input
D transformer
(A)
B-003-017-005 A power supply is to supply DC at 12 volts at 5 amperes. The power transformer should be rated higher than:
A 60 watts
B 17 watts
C 2.4 watts
D 6 watts

(C)
B-005-011-001 If no load is attached to the secondary winding of a transformer, what is current in the primary winding called?
A Latent current
B Stabilizing current
C Magnetizing current
D Direct current

(D)
B-005-011-002 A transformer operates a 6.3 volt 2 ampere light bulb from its secondary winding. The input power to the primary winding is approximately:
A 6 watts
B 8 watts
C 3 watts
D 13 watts

(C)
B-005-011-003 A transformer has a 240 volt primary that draws a current of 250 milliamperes from the mains supply. Assuming no losses and only one secondary, what current would be available from the 12 volt secondary?
A 25 amperes
B 50 amperes
C 5 amperes
D 215 amperes

(D)
B-005-011-004 In a mains power transformer, the primary winding has 250 turns, and the secondary has 500. If the input voltage is 120 volts, the likely secondary voltage is:
A 480 V
B 610 V
C 26 V
D 240 V

(D)
B-005-011-008 A 100% efficient transformer has a turns ratio of 1/5. If the secondary current is 50 milliamperes, the primary current is:
A 2 500 mA
B 0.01 A
C 0.25 mA
D 0.25 A

(A)
B-005-011-011 The fact that energy transfer from primary to secondary windings in a power transformer is not perfect is indicated by:
A warm iron laminations
B electrostatic shielding
C large secondary currents
D high primary voltages

Rectifier

(B)

B-003-008-003 In a regulated power supply, the _______________ is between the transformer and the filter.
A regulator
B rectifier
C input
D output

(A)
B-003-008-005 In a regulated power supply, the output of the filter connects to the ____________________.
A regulator
B transformer
C rectifier
D output

(B)
B-003-017-006 The diode is an important part of a simple power supply. It converts AC to DC, since it:
A allows electrons to flow in only one direction from anode to cathode
B allows electrons to flow in only one direction from cathode to anode
C has a high resistance to AC but not to DC
D has a high resistance to DC but not to AC

(C)
B-003-017-007 To convert AC to pulsating DC, you could use a:
A capacitor
B resistor
C diode
D transformer

(A)
B-004-002-004 The action of changing alternating current to direct current is called:
A rectification
B amplification
C transformation
D modulation

(A)

B-004-002-005 The electrodes of a semiconductor diode are known as:
A anode and cathode
B gate and source
C collector and base
D cathode and drain

(B)
B-004-002-006 If alternating current is applied to the anode of a diode, what would you expect to see at the cathode?
A Pulsating alternating current
B Pulsating direct current
C No signal

(A)
B-004-002-007 In a semiconductor diode, electrons flow from:
A cathode to anode
B anode to cathode
C cathode to grid
D grid to anode

(A)
B-004-002-008 What semiconductor device glows different colours, depending upon its chemical composition?
A A light-emitting diode
B A fluorescent bulb
C A neon bulb
D A vacuum diode

(A)
B-004-002-010 In order for a diode to conduct, it must be:
A forward-biased
B close coupled
C enhanced
D reverse-biased

Filter

(C)

B-003-008-004 In a regulated power supply, the output of the rectifier is connected to the ______________.
A transformer
B regulator
C filter
D output

(A)
B-003-017-004 What may cause a buzzing or hum in the signal of an AC-powered transmitter?
A A bad filter capacitor in the transmitter's power supply
B Using an antenna which is the wrong length
C Energy from another transmitter
D Bad design of the transmitter's RF power output circuit

(D)
B-003-017-011 You have a very loud low-frequency hum appearing on your transmission. In what part of the transmitter would you first look for the trouble?
A The variable-frequency oscillator
B The driver circuit
C The power amplifier circuit
D The power supply

Regulator

(C)

B-004-002-001 Zener diodes are used as:
A RF detectors
B AF detectors
C voltage regulators
D current regulators

(A)
B-004-002-003 The primary purpose of a Zener diode is to:
A regulate or maintain a constant voltage
B provide a voltage phase shift
C to boost the power supply voltage
D provide a path through which current can flow

(A)
B-004-002-009 Voltage regulation is the principal application of the:
A Zener diode
B junction diode
C light-emitting diode
D vacuum diode