Question: Which of the following rectifiers are primarily used for charging of low voltage batteries from AC supply ?

• 1. Mechanical rectifiers
• 2. Copper oxide rectifiers
• 3. Selenium rectifiers
• 4. Electrolytic rectifiers

Question: The efficiency of an electrolytic rectifier is nearly____________?

• 1. 80%
• 2. 70%
• 3. 60%
• 4. 40%

Question: The ignited or auxiliary anode in mercury arc rectifier is made of____________?

• 1. graphite
• 2. boron carbide
• 3. aluminium
• 4. copper

Question: he retentivity (a property) of material is useful for the construction of_______________?

• 1. permanent magnets
• 2. transformers
• 3. non-magnetic substances
• 4. electromagnets

Question: A permanent magnet______________?

• 1. attracts some substances and repels others
• 2. attracts all paramagnetic substances and repels others
• 3. attracts only ferromagnetic substances
• 4. attracts ferromagnetic substances and repels all others

Question: The relative permeability of materials is not constant:

• 1. diamagnetic
• 2. paramagnetic
• 3. ferromagnetic
• 4. insulating

Question: A rectangular magnet of magnetic moment M is cut into two piece of same length, the magnetic moment of each piece will be______________?

• 1. M
• 2. M/2
• 3. 2 M
• 4. M/4

Question: Magnetic moment is a_____________?

• 1. pole strength
• 2. universal constant
• 3. scalar quantity
• 4. vector quantity

Question: Hysteresis loop in case of magnetically hard materials is more in shape as compared to magnetically soft materials:

• 1. circular
• 2. triangular
• 3. rectangular
• 4. none of the above

Question: A keeper is used to_____________?

• 1. change the direction of magnetic lines
• 2. amplify flux
• 3. restore lost flux
• 4. provide a closed path for flux