Title: Diodes and Power Supplies
Course: Electronics Theory (IC 102-IC 102) > Section: Assessments

Q: A filter circuit is used to smooth out the ripple voltage at the AC output of the rectifier circuit.
- True
- False
A: False

Q: A single-phase full-wave rectifier is easier to filter than a three-phase full-wave rectifier
- True
- False
A: False

Q: After the prime source of power has been rectified, it is filtered to provide direct current suitable for operating the equipment.
- True
- False
A: True

Q: A full-wave power supply is to be operated off the line voltage with a step-down transformer to supply 60 Volts AC RMS across the secondary. What is the voltage output DC to the load (assume it is filtered)?
- 30 V
- 42 V
- 60 V
- 85 V
A: 30 V

Q: Although current is blocked in reverse bias
- there is some current due to majority carriers
- there is a very small current due to minority carriers
- there is and avalanche current
A: there is some current due to majority carriers

Q: Each atom in a Silicon crystal has
- four valence electrons
- four conduction electrons
- eight valence electrons, four of its own and four shared
- no valence electrons because all are shared with other atoms
A: four valence electrons

Q: For a Silicon diode, the value of the forward bias voltage typically
- is around 0.3 volts
- is around 0.7 volts
- depends on the width of the depletion region
- depends on the concentration of majority carriers
A: is around 0.3 volts

Q: Holes in an N-type semiconductor are
- minority carriers that are thermally produced
- minority carriers that are produced by doping
- majority carriers that are thermally produced
- majority carriers that are produced by doping
A: minority carriers that are thermally produced

Q: If you are checking a 60 Hz full-wave bridge rectifier and observe that the output has a 60 Hz ripple,
- the circuit is working properly
- the transformer secondary is shorted
- there is an open diode
- the filter capacitor is leaky
A: the circuit is working properly

Q: In the same half-wave rectifier as the above question, the diode must be able to withstand a reverse voltage of
- 10 V
- 5 V
- 20 V
- 3.18 V
A: 10 V

Q: Recombination is when
- an electron falls into a hole
- a positive and a negative ion bond together
- a valence electron becomes a conduction electron
- a crystal is formed
A: an electron falls into a hole

Q: The current in a semiconductor is produced by
- electrons only
- holes only
- negative ions
- both electrons and holes
A: electrons only

Q: The ideal DC output voltage of a capacitor-input filter (capacitor from rectifier output to ground) is equal to
- the peak value of the rectified voltage
- the average value of the rectified voltage
- the RMS value of the rectified voltage
A: the peak value of the rectified voltage

Q: The majority carriers in an N-type semiconductor are
- holes
- electrons
- protons
- neutrons
A: holes

Q: The peak value of the input to a half-wave rectifier is 10V. The approximate peak value of the output is
- 10 V
- 3.18 V
- 10.7 V
- 9.3V
A: 10 V

Q: The positive lead of an ohmmeter is connected to the anode of a diode and the negative lead is connected to the cathode. The diode is
- reverse biased
- open
- forward biased
- faulty
- answers B and D
A: reverse biased

Q: The ripple frequency of a half-wave power supply is
- 30 Hz
- 60 Hz
- 120 Hz
- 240 Hz
A: 30 Hz

Q: The term bias means
- the ratio of majority carriers to minority carriers
- the amount of current across the PN junction
- a DC voltage is applied to control the operation of a device
A: the ratio of majority carriers to minority carriers

Q: To forward bias a PN junction diode
- an external voltage is applied that is positive at the anode and negative at the cathode
- an external voltage is applied that is negative at the anode and positive at the cathode
A: an external voltage is applied that is positive at the anode and negative at the cathode

Q: When a 60 Hz sinusoidal voltage is applied to the input of a three phase full-wave bridge rectifier, the output frequency is
- 60 Hz
- 120 Hz
- 240 Hz
- 360 Hz
A: 60 Hz

Q: When a PN junction is forward biased
- the only current is hole current
- the only current is electron current
- the only current is produced by majority carriers
- the current is produced by both holes and electrons
A: the only current is hole current

Q: When a voltmeter is place across a forward biased diode, it will read a voltage approximately equal to
- the bias battery voltage
- zero volts
- the diode barrier potential
- the total circuit voltage
A: the bias battery voltage

Q: When forward biased, a diode
- blocks current
- conducts current
- has a high resistance
- drops a large voltage
A: blocks current

Q: When the peak output voltage is 100V, the PIV for each diode in a center-tapped full-wave rectifier is (neglecting the diode drop).
- 100 V
- 200 V
- 141 V
- 50 V
A: 100 V

Q: What is the voltage drop across the 330 Ohm resistor?
A: 9.3 V