Question: is an element used in semiconductors whose atoms have three valence electrons?

• 1. An acceptor
• 2. A donor
• 3. Germanium
• 4. Silicon

Question: For germanium the forbidden energy gap is_______________?

• 1. 0.15 eV
• 2. 0.25 eV
• 3. 0.5eV
• 4. 0.7eV

Question: The current due to electron flow in conduction band is the hole current in valence band?

• 1. equal to
• 2. less than
• 3. greater than
• 4. any of the above

Question: The minority carrier concentration is largely a function of_____________?

• 1. forward biasing voltage
• 2. reverse biasing voltage
• 3. temperature
• 4. the amount of doping

Question: is usually used for brush rockers____________?

• 1. Mild steel
• 2. Copper
• 3. Aluminium
• 4. Cast-iron

Question: The stator of a D.C. machine comprises of_____________?

• 1. main poles
• 2. interpoles
• 3. frame
• 4. all of the above

Question: Which of the following in an application of D.C. motors?

• 1. Traction
• 2. Drives for process industry
• 3. Battery driven vehicles
• 4. All of the above

Question: The cylindrical windings using circular conductors are used for current rating of____________?

• 1. upto 20 A
• 2. upto 40 A
• 3. upto 60 A
• 4. upto 80 A

Question: The laminations of the armature of a D.C. machine are usually ___________ thick?

• 1. 0.1 to 0.2 mm
• 2. 0.2 to 0.3 mm
• 3. 0.3 to 0.4 mm
• 4. 0.4 to 0.5 mm

Question: ___________ brushes are fragile and cause excessive wear of commutator?

• 1. Natural graphite
• 2. Hard carbon
• 3. Electro graphitic
• 4. Metal graphite