CWB Level 2 Study Questions and Verified Answers Test
1. In parallel electrical circuits, the voltage across each resistor is the same
since each path is connected to the same voltage source. Select the correct
statement.
A. in each parallel path the resistance must be equalized to create equal
voltage.
B. the current flowing in each parallel path must be the same as the voltage.
C. the current flowing in each parallel path depends on the resistance in
each path
D. the current flowing in each parallel path depends on the capacitance in each
path: C. the current flowing in each parallel path depends on the resistance in each
path
2. The duty cycle of a welding power supply is based upon delivering its rated
output for a given number of minutes. Which of the following statements is
correct.
A. a 300 amp/60% duty cycle machine is rated to deliver 300 amps for 6 minutes
in a ten minute period
B. a 300 amp/30% duty cycle machine is rated to deliver 300 amps in a ten
minute period
C. a 250 amp/30% duty cycle machine is rated to deliver 250 amps for 30
minutes separated by 10 minutes at rest
D. a 300 amp/60% duty cycle machine is rated to deliver 500 amps maximum
for 6 minutes in a ten minute period: A. a 300 amp/60% duty cycle machine is
rated to deliver 300 amps for 6 minutes in a ten minute period
3. Conventional transformer-rectifiers;
A. convert direct current into alternating current
B. convert alternating current into direct current
C. convert alternating current into pulsed current
D. convert direct current into pulsed current: B. convert alternating current into
direct current
4. A conventional diode placed in a circuit allows the passage of current in one
direction only. A silicon controlled rectifier(SCR) operates slightly differently.
How does it work?
A. an SCR conducts current in both directions until turned on and current flow
is then prevented
B. an SCR is non-conductive until turned onland then allows current to flow
in both directions
C. an SCR is non-conductive until turned on, allowing current to flow in one
, CWB Level 2 Study Questions and Verified Answers Test
direction only until the flow of current stops: C. an SCR is non-conductive until
turned on, allowing current to flow in one direction only until the flow of current stops
5. What is the term for voltage measured across the output terminals of a
welding machine when no current is being drawn?
A. diode voltage
B. operating voltage
C. open circuit voltage
D. terminal voltage: C. open circuit voltage
6. A 60% duty cycle means that the power supply can deliver its rated output
for:
A 60% of the rated output only
B. 60% over the rated output followed by 4 minutes at rest
C. 6 minutes at rest followed by 4 minutes at rated output
D. 6 minutes at rated output followed by 4 minutes at rest: D. 6 minutes at rated
output followed by 4 minutes at rest
7. One of the simplest ways of controlling the output of a welding transformer
is to change the efficiency of coupling between the primary and secondary
coils. How can this be done?
A) slide a piece of wood between the primary and the secondary coils
B) design the transformer with either a moving core or moving primary coils
C) design the transformer with a number of taps to select different output
curves
D) use the timed firing of SCR's to control total conduction time: B. design the
transformer with either a moving core or moving primary coils
8. When choosing between AC and DC output;
A. the process generally determines the type of current
B. high current output machines are always both AC/DC
C. DC is generally used for very high output applications
D. most supplies are equipped with constant voltage/constant current op-
tions: A. the process generally determines the type of current
9. Which of the following metals has the lowest electrical resistivity?
A aluminum
B. tungsten
C. copper
D. iron: C. copper
, CWB Level 2 Study Questions and Verified Answers Test
10. What is the purpose of an inverter?
A. to convert AC current to DC current of the same frequency
B. to convert DC current to high frequency AC current
C. to convert AC current to DC current
D. to convert electrode positive to electrode negative: C. to convert AC current
to DC current
11. Which of the following methods is commonly used to control the output of
a transformer?
A. an auxiliary power supply which feeds the secondary as required
B. a saturable reactor in series with the output
C. resistance placed in parallel with the primary of the transformer
D. taps on the secondary of the transformer: D. taps on the secondary of the
transformer
12. A transformer type welding power source without a rectifier outputs what
type of current?
A. direct current
B. alternating current
C. high frequency current
D. pulsed direct current: B. alternating current
13. When gas tungsten arc welding steels electrode polarity is most common-
ly;
A. electrode positive
B. electrode negative
C. alternating current
D. electrode square wave: B. electrode negative
14. A disadvantage of SCR control is that the output is very 'choppy'. How is
the output made more suitable for welding?
A. the output is smoothed out by the addition of capacitors
B. the large inductor or choke will be added to the circuit
C. the output from an SCR bridge is smooth enough for welding purposes
D. the diodes added to all SCR controlled machines to prevent "choppy"
output: A. the output is smoothed out by the addition of capacitor
15. Gas tungsten arc and plasma arc welding power sources are commonly
designed with high frequency units. What does the high frequency unit do?
A. increases heat input due to the increased frequency which increases the
total time at high current flow.
B. outputs high voltage, low current to create and maintain a stable conductive
path for the flow of power.
C. decreases the cleaning action created by electrode negative polarity pre-
, CWB Level 2 Study Questions and Verified Answers Test
sent in alternating current arcs.: B. outputs high voltage, low current to create and
maintain a stable conductive path for the flow of power
16. Gases are not normally electrically conductive. To start an arc;
A. requires high voltage
B. requires high inductance
'C. requires high current
D. requires AC power: A. requires high voltage
17. What voltage is required to cause 5 amps of current to flow through a
resistance of 22 ohms?
A. 110 volts
B. 0.22 volts
C. 4.4 volts
D. 5 volts: A. 110 volts
18. What type of output is usually required for Gas Tungsten Arc Welding?
A. constant voltage
B. high frequency
C. low power factor
D. low duty cycle
E. constant current: E. constant current
19. In GTAW, the high frequency unit increases the incoming AC line voltage
to several thousand volts. Select the correct statement.
A. systems are limited to less than 4,000 volts for safety reasons
B. the spark gap needs to be at least 75mm (3") wide for the spark to create
the arc
C. high frequency systems output high voltage but only at low current flow
D. high frequency systems only work with inverter based direct current arcs: C.
high frequency systems output high voltage but only at low current flow
20. How is a thyrister or SCR (silicon controlled rectifier) turned on?
A. by reversing current through the junction
B. by a signal called a "gate pulse"
C. SCR's must be switched mechanically
D. by a capacitor linked to a high frequency generator: B. by a signal called a
"gate pulse"
21. If a transformer secondary coil has fewer turns than the primary coil, it is
described as;
A. an autotransformer
B. a step-up transformer
C. a step-down transformer
D. a rectifying transformer: C. a step-down transformer
1. In parallel electrical circuits, the voltage across each resistor is the same
since each path is connected to the same voltage source. Select the correct
statement.
A. in each parallel path the resistance must be equalized to create equal
voltage.
B. the current flowing in each parallel path must be the same as the voltage.
C. the current flowing in each parallel path depends on the resistance in
each path
D. the current flowing in each parallel path depends on the capacitance in each
path: C. the current flowing in each parallel path depends on the resistance in each
path
2. The duty cycle of a welding power supply is based upon delivering its rated
output for a given number of minutes. Which of the following statements is
correct.
A. a 300 amp/60% duty cycle machine is rated to deliver 300 amps for 6 minutes
in a ten minute period
B. a 300 amp/30% duty cycle machine is rated to deliver 300 amps in a ten
minute period
C. a 250 amp/30% duty cycle machine is rated to deliver 250 amps for 30
minutes separated by 10 minutes at rest
D. a 300 amp/60% duty cycle machine is rated to deliver 500 amps maximum
for 6 minutes in a ten minute period: A. a 300 amp/60% duty cycle machine is
rated to deliver 300 amps for 6 minutes in a ten minute period
3. Conventional transformer-rectifiers;
A. convert direct current into alternating current
B. convert alternating current into direct current
C. convert alternating current into pulsed current
D. convert direct current into pulsed current: B. convert alternating current into
direct current
4. A conventional diode placed in a circuit allows the passage of current in one
direction only. A silicon controlled rectifier(SCR) operates slightly differently.
How does it work?
A. an SCR conducts current in both directions until turned on and current flow
is then prevented
B. an SCR is non-conductive until turned onland then allows current to flow
in both directions
C. an SCR is non-conductive until turned on, allowing current to flow in one
, CWB Level 2 Study Questions and Verified Answers Test
direction only until the flow of current stops: C. an SCR is non-conductive until
turned on, allowing current to flow in one direction only until the flow of current stops
5. What is the term for voltage measured across the output terminals of a
welding machine when no current is being drawn?
A. diode voltage
B. operating voltage
C. open circuit voltage
D. terminal voltage: C. open circuit voltage
6. A 60% duty cycle means that the power supply can deliver its rated output
for:
A 60% of the rated output only
B. 60% over the rated output followed by 4 minutes at rest
C. 6 minutes at rest followed by 4 minutes at rated output
D. 6 minutes at rated output followed by 4 minutes at rest: D. 6 minutes at rated
output followed by 4 minutes at rest
7. One of the simplest ways of controlling the output of a welding transformer
is to change the efficiency of coupling between the primary and secondary
coils. How can this be done?
A) slide a piece of wood between the primary and the secondary coils
B) design the transformer with either a moving core or moving primary coils
C) design the transformer with a number of taps to select different output
curves
D) use the timed firing of SCR's to control total conduction time: B. design the
transformer with either a moving core or moving primary coils
8. When choosing between AC and DC output;
A. the process generally determines the type of current
B. high current output machines are always both AC/DC
C. DC is generally used for very high output applications
D. most supplies are equipped with constant voltage/constant current op-
tions: A. the process generally determines the type of current
9. Which of the following metals has the lowest electrical resistivity?
A aluminum
B. tungsten
C. copper
D. iron: C. copper
, CWB Level 2 Study Questions and Verified Answers Test
10. What is the purpose of an inverter?
A. to convert AC current to DC current of the same frequency
B. to convert DC current to high frequency AC current
C. to convert AC current to DC current
D. to convert electrode positive to electrode negative: C. to convert AC current
to DC current
11. Which of the following methods is commonly used to control the output of
a transformer?
A. an auxiliary power supply which feeds the secondary as required
B. a saturable reactor in series with the output
C. resistance placed in parallel with the primary of the transformer
D. taps on the secondary of the transformer: D. taps on the secondary of the
transformer
12. A transformer type welding power source without a rectifier outputs what
type of current?
A. direct current
B. alternating current
C. high frequency current
D. pulsed direct current: B. alternating current
13. When gas tungsten arc welding steels electrode polarity is most common-
ly;
A. electrode positive
B. electrode negative
C. alternating current
D. electrode square wave: B. electrode negative
14. A disadvantage of SCR control is that the output is very 'choppy'. How is
the output made more suitable for welding?
A. the output is smoothed out by the addition of capacitors
B. the large inductor or choke will be added to the circuit
C. the output from an SCR bridge is smooth enough for welding purposes
D. the diodes added to all SCR controlled machines to prevent "choppy"
output: A. the output is smoothed out by the addition of capacitor
15. Gas tungsten arc and plasma arc welding power sources are commonly
designed with high frequency units. What does the high frequency unit do?
A. increases heat input due to the increased frequency which increases the
total time at high current flow.
B. outputs high voltage, low current to create and maintain a stable conductive
path for the flow of power.
C. decreases the cleaning action created by electrode negative polarity pre-
, CWB Level 2 Study Questions and Verified Answers Test
sent in alternating current arcs.: B. outputs high voltage, low current to create and
maintain a stable conductive path for the flow of power
16. Gases are not normally electrically conductive. To start an arc;
A. requires high voltage
B. requires high inductance
'C. requires high current
D. requires AC power: A. requires high voltage
17. What voltage is required to cause 5 amps of current to flow through a
resistance of 22 ohms?
A. 110 volts
B. 0.22 volts
C. 4.4 volts
D. 5 volts: A. 110 volts
18. What type of output is usually required for Gas Tungsten Arc Welding?
A. constant voltage
B. high frequency
C. low power factor
D. low duty cycle
E. constant current: E. constant current
19. In GTAW, the high frequency unit increases the incoming AC line voltage
to several thousand volts. Select the correct statement.
A. systems are limited to less than 4,000 volts for safety reasons
B. the spark gap needs to be at least 75mm (3") wide for the spark to create
the arc
C. high frequency systems output high voltage but only at low current flow
D. high frequency systems only work with inverter based direct current arcs: C.
high frequency systems output high voltage but only at low current flow
20. How is a thyrister or SCR (silicon controlled rectifier) turned on?
A. by reversing current through the junction
B. by a signal called a "gate pulse"
C. SCR's must be switched mechanically
D. by a capacitor linked to a high frequency generator: B. by a signal called a
"gate pulse"
21. If a transformer secondary coil has fewer turns than the primary coil, it is
described as;
A. an autotransformer
B. a step-up transformer
C. a step-down transformer
D. a rectifying transformer: C. a step-down transformer
