General G7A: Power supplies and schematic symbols
These are the 13 official questions in group G7A of the 2023–2027 General question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- G7A01Question 1
What is the function of a power supply bleeder resistor?
- AIt acts as a fuse for excess voltage
- BIt discharges the filter capacitors when power is removed Correct
- CIt removes shock hazards from the induction coils
- DIt eliminates ground loop current
Why: A bleeder resistor discharges the filter capacitors when power is removed.
- G7A02Question 2
Which of the following components are used in a power supply filter network?
- ADiodes
- BTransformers and transducers
- CCapacitors and inductors Correct
- DAll these choices are correct
Why: Power supply filters use capacitors and inductors.
- G7A03Question 3
Which type of rectifier circuit uses two diodes and a center-tapped transformer?
- AFull-wave Correct
- BFull-wave bridge
- CHalf-wave
- DSynchronous
Why: Two diodes with a center-tapped transformer make a full-wave rectifier.
- G7A04Question 4
What is characteristic of a half-wave rectifier in a power supply?
- AOnly one diode is required Correct
- BThe ripple frequency is twice that of a full-wave rectifier
- CMore current can be drawn from the half-wave rectifier
- DThe output voltage is two times the peak input voltage
Why: A half-wave rectifier needs only one diode.
- G7A05Question 5
What portion of the AC cycle is converted to DC by a half-wave rectifier?
- A90 degrees
- B180 degrees Correct
- C270 degrees
- D360 degrees
Why: A half-wave rectifier uses half of each cycle: 180 degrees.
- G7A06Question 6
What portion of the AC cycle is converted to DC by a full-wave rectifier?
- A90 degrees
- B180 degrees
- C270 degrees
- D360 degrees Correct
Why: A full-wave rectifier uses the whole cycle: 360 degrees.
- G7A07Question 7
What is the output waveform of an unfiltered full-wave rectifier connected to a resistive load?
- AA series of DC pulses at twice the frequency of the AC input Correct
- BA series of DC pulses at the same frequency as the AC input
- CA sine wave at half the frequency of the AC input
- DA steady DC voltage
Why: Unfiltered full-wave output is DC pulses at twice the AC frequency.
- G7A08Question 8
Which of the following is characteristic of a switchmode power supply as compared to a linear power supply?
- AFaster switching time makes higher output voltage possible
- BFewer circuit components are required
- CHigh-frequency operation allows the use of smaller components Correct
- DInherently more stable
Why: Running at high frequency lets a switchmode supply use smaller components.
- G7A09Question 9
Which symbol in figure G7-1 represents a field effect transistor?
- ASymbol 2
- BSymbol 5
- CSymbol 1 Correct
- DSymbol 4
Why: Symbol 1 in G7-1 is a field-effect transistor.
- G7A10Question 10
Which symbol in figure G7-1 represents a Zener diode?
- ASymbol 4
- BSymbol 1
- CSymbol 11
- DSymbol 5 Correct
Why: Symbol 5 in G7-1 is a Zener diode.
- G7A11Question 11
Which symbol in figure G7-1 represents an NPN junction transistor?
- ASymbol 1
- BSymbol 2 Correct
- CSymbol 7
- DSymbol 11
Why: Symbol 2 in G7-1 is an NPN junction transistor.
- G7A12Question 12
Which symbol in Figure G7-1 represents a solid core transformer?
- ASymbol 4
- BSymbol 7
- CSymbol 6 Correct
- DSymbol 1
Why: Symbol 6 in G7-1 is a solid-core transformer.
- G7A13Question 13
Which symbol in Figure G7-1 represents a tapped inductor?
- ASymbol 7 Correct
- BSymbol 11
- CSymbol 6
- DSymbol 1
Why: Symbol 7 in G7-1 is a tapped inductor.