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

One-fifth of the batteries produced by an upstart factory are defective and one -quarter of all batteries produced are rejected by the quality control technician. If one-tenth of the non-defective batteries are rejected by mistake and if all the batteries not rejected are sold, then what percent of the batteries sold by the factory are defective?

A

4%

B

3%

C

6%

D

5%

The metal rectifiers are preferred to valve rectifiers due to which of the following advantages ?

A

They are mechanically strong

B

They do not require any voltage for filament heating

C

Both (A) and (B)

D

None of the above

The metal rectifiers, as compared to mercury arc rectifiers

A

operate on low temperatures

B

can operate on high voltages

C

can operate on heavy loads

D

give poor regulation

E

none of the above

সিরিজে সংযুক্ত একটি এ্যামিটার এবং একটি অজানা রোধ দুটি একই রকম 1.5 V ব্যাটারীর দুই প্রান্তে সংযুক্ত আছে। যখন ব্যাটারী দুটি সিরিজে সংযুক্ত থাকে তখন এ্যামিটার। amp রিডিং প্রদর্শন করে। আবার ব্যাটারী দুটি সমান্তরালে সংযুক্ত করলে 0.6 amp রিডিং প্রদর্শন করে। ব্যাটারীর আভ্যন্তরিন রোধ কত ? (An ammeter and an unknown resistance are connected in series across two identical batteries of each 1.5 V. The ammeter shows current I amp and 0.6 amp when the batteries are connected in series and parallel, respectively. What is the internal resistance of the battery?)

A

13Ω

B

12Ω

C

1Ω

D

0.1Ω

E

23Ω

In constant voltage charging method, the charging current from discharged to fully charged condition

A

decreases

B

increases

C

remains constant

D

none of the above

D.C. generator generally preferred for charging automobile batteries is

A

Series generator

B

Shunt generator

C

Long shunt compound generator

D

Any of the above

Under normal charging rate, the charging current should be

A

10% of capacity

B

20% of capacity

C

30% of capacity

D

40% of capacity

In constant-current charging method, the supply voltage from discharged to fully charged condition

A

decreases

B

increases

C

remains constant

D

none of the above

Which of the following rectifiers have been used extensively in supplying direct current for electroplating?

A

Copper oxide rectifiers

B

Selenium rectifiers

C

Mercury arc rectifiers

D

Mechanical rectifiers

E

None of the above

Mercury, in arc rectifiers, is chosen for cathode because

A

Its ionization potential is relatively low

B

Its atomic weight is quite high

C

Its boiling point and specific heat are low

D

All of the above

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

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