Deck 16: RL Circuits

Question 1

Most diodes are made from a semiconductor material called silicon.

Answer 1

True

Question 2

A zener diode is used as a constant voltage regulator.

Answer 2

True

Question 3

The ripple frequency of a half-wave rectifier equals the supply frequency.

Answer 3

True

Question 4

Photodiodes will conduct more as the light intensity upon them increases.

Question 5

Diode clampers cut off voltage above or below specified levels.

Question 6

A forward-biased silicon diode normally drops about 16 V.

Question 7

Ripple voltage is caused by the charging and discharging of the diodes.

Question 8

Zener diodes can conduct very large currents.

Question 9

A common name for a PN junction is the transistor.

Question 10

A forward-biased silicon diode normally drops about 0.7 V.

Question 11

Adding impurities to semiconductor materials is called doping.

Question 12

Reverse breakdown usually occurs when a diode is forward biased by about 0.7 V.

Question 13

Most diodes are made from a semiconductor material called germanium.

Question 14

A forward-biased germanium diode normally drops about 0.3 V.

Question 15

A half-wave rectifier uses four diodes as rectifiers.

Question 16

LEDs will emit light if a reverse voltage is applied to them.

Question 17

To rectify is to convert dc to pulsating ac.

Question 18

The movement of free electrons is called electron current.

Question 19

Current flow through a diode is normally caused by ________.

A)depletion layer breakdown
B)a reverse voltage across the diode
C)forward voltage across the diode
D)thermally produced electron-hole pairs

Question 20

Varactor diodes are used as voltage-variable capacitors.

Question 21

What is the current through R2 in Figure 16-1(c) if the diode is silicon?

A)0.7 mA
B)0 A
C)0.3 mA
D)25 mA

Question 22

If you measure the voltage across a diode and it measures 0.3 V, the diode is probably made of ________ and is ________ biased.

A)germanium, reverse
B)silicon, forward
C)germanium, forward
D)silicon, reverse

Question 23

If you measure 17 V across a diode, it is probably ________.

A)in heavy conduction
B)reverse biased
C)forward biased
D)shorted

Question 24

If the polarity of the silicon diode is reversed in Figure 16-1(c), is ________.

A)25 V
B)49.3 V
C)0.7 V
D)0 V

Question 25

What is the current through if the diode is silicon?

A)49.7 mA
B)49.3 mA
C)25 mA
D)0 A

Question 26

If the diode is silicon, what is the voltage across the resistor in Figure 16-1(a)?

A)0 V
B)20 V
C)0.7 V
D)19.3 V

Question 27

If an ohmmeter check of a diode indicates a high resistance in one direction and low resistance in the other, the diode is probably ________.

A)open
B)shorted
C)bad
D)good

Question 28

You test a diode with an ohmmeter. The two readings indicate a very low value of resistance. The diode is probably ________.

A)conducting heavily
B)open
C)normal
D)shorted

Question 29

If the diode is made of silicon in Figure 16-1(b), what is the current?

A)9.4 mA
B)0 A
C)10 mA
D)8.6 mA

Question 30

What is the voltage across if the diode is silicon?

A)49.3 V
B)50 V
C)25 V
D)49.7 V

Question 31

If the polarity of the source voltage is reversed in Figure 16-1(c), is ________.

A)49.3 V
B)0 V
C)0.7 V
D)25 V

Question 32

What is the voltage across the resistor in Figure 16-1(a) if the diode is germanium?

A)0.7 V
B)0 V
C)20 V
D)19.7 V

Question 33

If the diode opens in Figure 16-1(b), the voltage across the diode is ________.

A)4.3 V
B)0 V
C)0.7 V
D)1 V

Question 34

What is the current in Figure 16-1(b) if the diode is made of silicon and the polarity of the source voltage is reversed?

A)0.6 mA
B)5 mA
C)0 A
D)10 mA

Question 35

If the lead on an ohmmeter is connected to a diodeʹs anode and the lead on the ohmmeter is connected to the diodeʹs cathode, the measured resistance is normally ________.

A)very low
B)very high
C)
D)

Question 36

If the cathode voltage of a forward biased silicon diode is 4.5 V, what is the anode voltage?

A)0.7 V
B)-5.2 V
C)5.2 V
D)-0.7 V

Question 37

What is the voltage across the silicon diode in Figure 16-1(b)?

A)0.3 V
B)-0.7 V
C)1.0 V
D)0.7 V

Question 38

A forward biased silicon diode is in series with a 1 resistor. The source voltage is 5 V. The voltage across the diode is ________ and the voltage across the resistor is ________.

A)0.7 V, 4.3 V
B)0.3 V, 4.7 V
C)4.7 V, 0.3 V
D)4.3 V, 0.7 V

Question 39

To forward bias a silicon diode with -1.6 V on the anode, you must apply a voltage of ________ on the cathode.

A)-0.9 V
B)2.3 V
C)0.9 V
D)-2.3 V

Question 40

What is the current through if the diode is germanium?

A)49.3 mA
B)49.7 mA
C)25 mA
D)0 A

Question 41

If the measured resistance of a diode is very low in both directions, the diode is probably ________.

A)conducting heavily
B)normal
C)open
D)shorted

Question 42

If the cathode voltage of a forward-biased silicon diode equals 6.5 V, the anode voltage equals ________.

A)-0.7 V
B)7.2 V
C)-7.2 V
D)0.7 V

Question 43

In a semiconductor diode, the two bias conditions are ________.

A)forward and reverse
B)open and closed
C)positive and negative
D)blocking and non-blocking

Question 44

Materials whose molecules arrange themselves into a crystal structure are bound together by:

A)full valence shells.
B)covalent bonding.
C)sharing valence electrons.
D)all of these.

Question 45

To forward bias a silicon diode with a -71.6 V anode voltage, apply a ________ cathode voltage.

A)
B)
C)
D)

Question 46

Current through a diode is blocked by ________.

A)thermally produced electron-hole pairs
B)reverse voltage across the diode
C)forward voltage across the diode
D)depletion layer breakdown

Question 47

The forward bias on a P-N diode to make the diode conduct must be greater than the:

A)barrier potential.
B)conduction bond.
C)volence bond.
D)reverse bias.

Question 48

Applying the reverse breakdown voltage to a diode will ________.

A)cause it to act like a capacitor
B)never do any harm
C)cause it to act like a switch
D)usually damage the diode

Question 49

If you measure 0.7 V across a diode, the diode is probably made of ________ and is ________ biased.

A)germanium, reverse
B)silicon, forward
C)silicon, reverse
D)germanium, forward

Question 50

In a P-N diode, the region near the P-N junction is called:

A)the diffusion region.
B)the recombination region.
C)the neutral region.
D)the depletion region.

Question 51

When a diode is forward biased it is ________.

A)blocking current
B)conducting current
C)similar to an open switch
D)similar to a closed switch
E)both B and D

Question 52

Reverse breakdown current is carried by:

A)minority carriers.
B)pentavalent impurity atoms.
C)majority carrier.
D)trivalent impurity atoms.

Question 53

When the positive lead of an ohmmeter is connected to the cathode of a diode and the negative lead is connected to the anode, the meter reads ________.

A)an infinitely high resistance
B)a very low resistance
C)
D)a gradually increasing resistance

Question 54

The arrowhead in the schematic symbol for a diode represents:

A)the semiconductor lead.
B)the cathode.
C)the anode.
D)all of these.

Question 55

Doping a semiconductor material with pentavalent impurities results in:

A)P-type material.
B)N-P type material.
C)P-N type material.
D)N-type material.

Question 56

If the measured resistance of a diode is high in both directions, the diode is probably ________.

A)reverse biased
B)open
C)forward biased
D)shorted

Question 57

If a half-wave rectifier outputs 58 VP, the diodeʹs PIV should be more than ________.

A)116 V
B)15 V
C)29 V
D)58 V

Question 58

A DC voltage that sets the operating conditions of a semiconductor device is called the ________.

A)battery
B)bias
C)barrier potential
D)depletion voltage

Question 59

The PN junction is found in ________.

A)transistors
B)semiconductor diodes
C)all semiconductor materials
D)both A and B

Question 60

If a forward biased silicon diode is in series with a resistor and a 10 V source, the voltage across the diode is ________ and the voltage across the resistor is ________.

A)0.3 V, 9.7 V
B)9.7 V, 0.3 V
C)0.7 V, 9.3 V
D)9.3 V, 0.7 V

Question 61

A full-wave bridge rectifier requires ________.

A)four diodes and a transformer with a single secondary
B)a high voltage to operate it
C)two diodes and a transformer with a single secondary
D)a center-tapped transformer

Question 62

A full-wave rectifier requires ________.

A)two diodes and a center-tapped transformer
B)four diodes and a center-tapped transformer
C)a high voltage to operate it
D)two diodes and a transformer with a single secondary

Question 63

Which block in Figure 16-2 will change the amplitude of the ac voltage?

A)1
B)2
C)3
D)4

Question 64

The ripple voltage from a power supply ________.

A)varies with load
B)is very high
C)is about 1 V
D)is zero

Question 65

Which block in Figure 16-2 changes ac to pulsating dc?

A)1
B)2
C)3
D)4

Question 66

If a 75 VP sine wave is applied to a half-wave rectifier, the diodeʹs peak inverse voltage is ________.

A)37.5 V
B)75 V
C)150 V
D)0 V

Question 67

If the load current increases in a simple zener regulator, the ________.

A)total current increases
B)zener current decreases
C)current through the series resistor increases
D)voltage across the series resistor decreases

Question 68

If the load current decreases in a simple zener regulator, the ________.

A)zener current decreases
B)zener current increases
C)current through the series resistor decreases
D)voltage across the series resistor decreases

Question 69

If a full-wave rectifier outputs 38 VP, its average output equals ________.

A)76.7 V
B)38 V
C)19.3 V
D)24.2 V

Question 70

Which block will smooth out the pulsating dc in Figure 16-2?

A)1
B)2
C)3
D)4

Question 71

If the filter capacitor opens in Figure 16-2, ________.

A)the ripple voltage increases
B)a loud hum will be heard
C)the diodes would open
D)the output dc will be very low

Question 72

If a diode in a half-wave rectifier opens in Figure 16-2, ________.

A)the output dc voltage increases and the ripple frequency decreases
B)the output dc voltage decreases and the ripple voltage increases
C)the output dc voltage increases and the ripple voltage decreases
D)the output dc voltage decreases and the ripple voltage decreases

Question 73

If a diode in a full-wave rectifier opens, ________.

A)the dc output voltage will increase and the ripple frequency will decrease
B)the dc output voltage will decrease and the ripple frequency will decrease
C)the dc output voltage will decrease and the ripple voltage will decrease
D)the dc output voltage will increase and the ripple voltage will decrease

Question 74

If the diode in a half-wave rectifier shorts, the ________.

A)output voltage would be zero
B)output voltage would equal the transformer secondary voltage
C)output ripple would be very small
D)output voltage would not change

Question 75

If the filter capacitor becomes leaky in Figure 16-2, ________.

A)the ripple voltage will increase
B)the output dc will be very low
C)a loud hum will be heard
D)the diodes would open

Question 76

The purpose of Block 4 in Figure 16-2 is to ________.

A)keep the dc output voltage constant as the load changes
B)adjust the output voltage to the correct ac value
C)make sure that the fuse will not blow
D)maintain a constant output current when the load current changes

Question 77

If a 60 Hz sine wave is input to a half-wave rectifier, its output frequency is ________.

A)60 Hz
B)0 Hz
C)30 Hz
D)120 Hz

Question 78

Which block in Figure 16-2 will keep the output voltage nearly constant under varying load?

A)1
B)2
C)3
D)4

Question 79

If the source voltage increases in a simple zener regulator, ________.

A)the voltage across the zener increases
B)the voltage across the series resistor decreases
C)the load current increases
D)the zener current increases

Question 80

The output of Block 2 in Figure 16-2 is:

A)a steady DC voltage.
B)a pulsating DC voltage.
C)a steady DC current.
D)a pulsating AC voltage.