Batteries: Important Two Marks Questions and Answers

UNIT 5: Batteries

Two Marks Questions and Answers

1. What is a battery? How does it differ from a cell?

A battery is an arrangement of several electrochemical cells, connected in series, that can be used as a source of direct electric current.

Thus,

A Cell: Contains only one anode and cathode.

A Battery: Contains several anodes and cathodes.

2. What are the important requirement of a battery?

A useful battery should fulfil the following requirements

(i) It should be light and compact for easy transport.

(ii) It should have long life both when it is being used and when it is not used.

(iii) The voltage of the battery should not vary appreciably during its use.

3. Will the emf of a battery vary with size? Give reason.

 No, the emf (voltage) of a battery does not vary with size because,

(i) as per nernst equation emf varies only with concentration and nature of the ingredients.

(ii) the number of anode and cathode only determine o its voltage (emf) not the size of anode and cathode.

4. What is a primary battery? Give an example

(or)

What are primary cells?

Primary cells are cells in which the electrode and the electrode reactions cannot be reversed by passing an external electrical energy. The reactions occur only once and after use they become dead. Therefore, they are not chargeable.

Example: Leclanche's cell

5. What are secondary cells?

Secondary cells are cells in which the electrode reactions can be reversed by passing an external electrical energy. Therefore, they can be recharged by passing electric current and used again and again. These are also called Storage cells (or) Accumulators.

Example: Lead acid storage cell, NiCd cell.

6. Write the cell representation of lead storage cell.

The cell may be represented as;

Pb / PbSO₄ // H₂SO₄ (aq)/PbO₂/Pb

7. State the reaction when a lead storage battery is recharged.

The cell can be recharged by passing electric current in the opposite direction. The electrode reaction gets reversed. As a result, Pb is deposited on anode and PbO₂ on the cathode. The density of H₂SO₄ also increases.

The net reaction during charging is

2PbSO₄(s) + 2H₂O + Energy ←^charging_discharging→ Pb(s) + PbO₂(s) + 2H₂SO₄(eq)

8. Write the charging and discharging reaction of lead accumulator.

Pb(s) + PbO₂(s) + 2H₂SO₄(aq) ←^charging_discharging→ 2PbSO₄ (s) + 2H₂O + Energy

9. What are the applications of lead acid storage cell?

(i) Lead storage cell is used to supply current mainly in automobiles such as cars, buses, trucks, etc.,

(ii) It is also used in gas engine ignition, telephone exchanges, hospitals, power stations, etc.,

10. What are the advantages of storage batteries?

(i) It is made easily.

(ii) It produces very high current.

(iii) The self‒discharging rate is low.

(iv) It also acts effectively at low temperature.

11. What is lithium‒ion battery?

Lithium‒ion battery is a secondary battery. As in lithium cell, it does not contain metallic lithium as anode. As the name suggests, the movement of lithium ions are responsible for charging and discharging.

12. What are the components of LIB?

• A positive electrode (Layers of lithium‒metal oxide) (cathode)

• A negative electrode (Layers of porous carbon) (anode)

• An electrolyte (Polymer gel) (separator)

13. What are the advantages of lithium cell?

 (i) Lithium‒ion batteries are high voltage and light weight batteries.

(ii) It is smaller in size.

(iii) It produces three time the voltage of Ni‒Cd batteries.

(iv) It has none of the memory effect seen in Ni‒Cd batteries.

14. What are the uses of lithium‒ion battery?

It is used in cell phone, note PC, portable LCD TV, semiconductor driven audio, etc.,

15. What are the components of leclanche's cell?

Anode: Zinc

Cathode: Carbon rod (graphite)

Electrolyte: (NH₄Cl + ZnCl₂ + MnO₂ + Starch + H₂O) paste

Emf: 1.5 V

16. What are the advantages of leclanche's cell?

1. The cost of dry cell is cheap and easily available.

2. The compact size of it makes it suitable for powering small electronic devices.

3. The electrolyte used in dry cell is not harmful and no leakage.

4. It is easy and safe for transportation.

17. What are the disadvantages of leclanche's cell?

1. This dry cell does not have an indefinite life, because NH₄Cl being acidic corrodes the zinc container, even if it is not used.

2. When current is drawn rapidly from it, products build up on the electrodes, so voltage drop occurs.

3. This cell can not be recharged.

4. Voltage decreases with continuous usage.

18. What are the uses of dry cell.

It is used in transistor radios, calculators, Flash lights, torches etc.,

19. What are the components of alkaline battery?

Anode: Zinc

Cathode: Carbon rod (graphite)

Electrolyte : (Zn powder + KOH + MnO₂ + Starch + H₂O) paste

Emf: 1.5 V

20. What are the advantages of alkaline battery.

(i) Zinc does not dissolve readily in a basic medium.

(ii) The life of alkaline battery is longer than the dry battery, because there is no corrosion on Zn.

(iii) Alkaline battery maintains its voltage, as the current is drawn from it.

21. Write the cell diagram of Nicad battery.

It is represented as:

  Cd | Ca(OH)₂ || KOH_(aq) | NiO₂ | Ni

22. What are the advantages of Nicad battery.

1. It is smaller and lighter.

2. It has longer life than lead storage cell.

3. Like a dry cell, it can be packed in a sealed container.

23. What is meant by battery pack? How is it usefull?

Battery pack generally refers to a collection of batteries that are assembled together to provide more power. Battery packs can be used in various applications such as in electric vehicles, power tools (or) as part of larger systems.

24. What are the important steps involved in the design of battery pack?

Step 1: Select the battery cell technology and the pack specifications by battery sizing.

Step 2: Battery pack designing (electrical, control and structural)

Step 3: Battery pack safety and testings.

25. How to calculate battery pack size?

The battery pack size (S) can be calculated by

S = VA'

where,

V = Voltage (obtained from above equation)

A' = Ampere rating of the cells

26. Write any two advantages of battery pack.

1. Primary advantage is portability and convenience.

2. It stores energy for later use and provide backup power during outages.

27. Write any two disadvantages of battery pack.

1. Battery packs are expensive to purchase.

2. Lifespan is limited.

28. What is meant by battery materials?

Battery materials refers to the various components that make up a battery. It includes variety of components including anode, cathode, electrolyte and separator.

29. What are the main parameters for a better battery performance?

(i) Capacity

(ii) Voltage

(iii) Energy density

(iv) Power

(v) Cycle life

(vi) Self‒discharging rate

(vii) Internal resistance

30. What is cycle‒life?

Cycle‒life determines the number of charge and discharge cycles a battery can undergo before its capacity degrades significantly.

31. What are SOC and DOD?

State of charge (SOC)

The amount of charge remaining in the battery is expressed as a percentage of its total capacity.

Depth of discharge (DOD)

It is the percentage of a battery's capacity that has been discharged.

32. What is C‒rate?

It refers to how quickly its stored energy is released. 1C rate indicating a full discharge in one hour.

33. What is the importance of battery testing?

These tests assess different aspects like capacity, output characteristics, efficiency, endurance and safety under various conditions.

34. What are the main aspects of battery safety?

The main aspects include propor handling, storage, charging and disposal.