1. Which of the following is NOT a type of resistance welding?
A) Carbon arc welding
B) Percussion welding
C) Spot welding
D) Butt welding
Answer: A
Explanation: Carbon arc welding uses an electric arc between a carbon electrode and the workpiece, differing from resistance welding methods.
2. In arc welding, arc blow can be minimized by:
A) Using bare electrodes
B) Welding away from the earth ground connection
C) Using AC welding machines
D) Increasing arc length
Answer: C
Explanation: AC welding machines help reduce arc blow by alternating the current direction, balancing magnetic fields.
3. Which shielding gas is known to produce deeper penetration and faster welding speeds?
A) Argon
B) Helium
C) Carbon dioxide
D) Nitrogen
Answer: B
Explanation: Helium provides deeper penetration and higher welding speeds due to its higher thermal conductivity.
4. Why is welding not performed directly from supply mains?
A) Customary use of welding machines
B) Excessive voltage
C) Voltage fluctuations
D) Impracticality of drawing heavy currents
Answer: D
Explanation: Direct welding from supply mains is impractical due to the high current requirements, which could overload the system.
5. In ultrasonic welding, the typical frequency range is:
A) 2,000 to 3,000 Hz
B) 30,000 to 40,000 Hz
C) 4,000 to 20,000 Hz
D) 50,000 to 80,000 Hz
Answer: B
Explanation: Ultrasonic welding typically operates in the 30,000 to 40,000 Hz range, facilitating effective bonding through high-frequency vibrations.
6. Which welding process does not require shielding gas?
A) Gas metal arc welding
B) Plasma arc welding
C) Shielded metal arc welding
D) Submerged arc welding
Answer: C
Explanation: Shielded metal arc welding (SMAW) uses a flux-coated electrode that produces its own shielding gas when heated.
7. What is the primary function of flux in welding?
A) Stabilize the arc
B) Prevent oxidation
C) Add alloying elements
D) All of the above
Answer: D
Explanation: Flux serves multiple purposes: stabilizing the arc, preventing oxidation by producing a shielding gas, and sometimes adding alloying elements to the weld.
8. In resistance welding, heat generation is directly proportional to:
A) Current
B) Voltage
C) Resistance
D) Current squared times resistance
Answer: D
Explanation: Heat generated (H) in resistance welding follows the formula H = I²Rt, indicating it's proportional to the square of the current times resistance and time.
9. Which of the following is a characteristic of a good weld?
A) Uniform bead
B) Lack of porosity
C) Adequate penetration
D) All of the above
Answer: D
Explanation: A quality weld exhibits a uniform bead, is free from porosity, and has sufficient penetration to ensure joint strength.
10. Which type of welding machine provides both AC and DC output?
A) Transformer only
B) Generator only
C) Transformer/rectifier
D) Plasma
Answer: C
Explanation: Transformer/rectifier welding machines are versatile, offering both AC and DC outputs for various welding applications