This document provides an overview of current electricity topics including definitions of cells and batteries, types of cells like simple voltage cells, wet Leclanche cells, and dry cells. It discusses how cells work and how cells can be combined in series and parallel. It also summarizes thermal effects of current, electrolysis, electrolytic burns, ionization of gases, thermionic emission, diodes, triodes, and electronic tubes.

1. “Current Electricity”
Presented by “insha ur rahman”
Presented to “Mam Fauzia”
Date:27-Jan-2020
Medical physic’s
“DPT”-Batch-1

2. Content:
• Definition of cells and battery.
• Simple voltage cell
• Wet lachlanche cell
• Dry lanclanche cell
• Combination of cells in series
• Combination of cells in parallel.
• Thermal effect of current
• Electrolysis and electrolytic burns.
• Ionization of gases and thermionic emission.
• Electronic tubes .
• Diodes and Triodes.

3. Batteries and cells:
• Cells and batteries are the which convert the chemical energy into
electrical energy in order to supply .
• There are two types of cells and batteries
• Primary and secondary.

5. Simple voltage cell:
• Definition:
• It is an apparatus which is used to provide electricity.
• Principle :
• Chemical energy changes to electrical energy.
• Construction:
• It consist of two strips one is zinc (cathod) and other is of
copper (Anode) placed in vessel containing dilute sulphuric
acid
• Both strips are connected to copper wires

7. • Working:
• When the zinc strips is placed in the acid solution it reacts
with the acid start to dissolve in it , so zinc atoms leave two
electrons .
• Zn Zn + 2e’s
• By which the Hydrochloric acid solution also become break
into Hydrgen ion H+ and sulphite SO4.
• These hydrogen ions takes electrons to copper plate , the
plate become positively charged .
• A current will start to pass from positive to electrode of cell
and the bulb is lighted .

8. Wet Leclanche Cell:
• Definition:
• A primary electrochemical cell having a zinc cathode in
contact with zinc chloride, ammonium chloride (as a solution
or a paste) as the electrolyte, and a carbon anode in contact
with a mixture of manganese dioxide and carbon powder.
• Construction:
• It is consists of the positive carbon electrode packed into a
mixture of MnO2 and powder carbon in a porous pot.
• The porous pot stands in a glass jar filled with a solution of
NH4-CL .
• The negative zinc electrode is dipped in the solution of NH4-
CL.

10. • Working:
• When the carbon and zinc rod is added to the circuit then in contact with
electrolytes, zinc atoms are ionized by giving two electrons.
• Zn → Zn2+ + 2e-
• Ammonium chloride (NH4Cl) in the electrolyte is thus ionized:
• 2NH4Cl → 2NH4
+ + 2Cl-
• Zinc ions make zinc chloride combined with chlorine ions.
• Zn2+ + 2Cl- → ZnCl3
• Ammonium ions (NH4
+) flow towards the carbon rod and become Indifferent by
taking an electron from the carbon rod, ammonium is converted into hydrogen
gas.
• 2NH4
+ + 2e- → 2NH3 + H2
• Manganese dioxide converts hydrogen gas into water, which does not cause the
action of polarization.
• 2MnO2 + H2 → Mn2O3 + H2O
• Full Reaction
• Zn + 2NH4Cl + 2MnO2 → ZnCl2 + 2NH3 + Mn2O3 + H2O + Energy [3]
• Thus, the excess of electrons on the zinc rod and the lack of electrons on the
carbon rod decreases, whereby the potentiality of carbon rod becomes more than
zinc rod potential. So the electrons start flowing towards the carbon rod from zinc
rod. The Electromotive force of the cell is 1.5 volt.

11. Dry leclanche cell:
• Introduction:
• The Dry Cell was discovered by French Scientist G. Leclanche in 1868.
• It is the most common cell which is the improved version of Leclanche
Cell.
• It is a portable cell and free from liquid. This is why, it is called dry cell as
it do not contain any liquid.
• Dry Cell is widely used in our day to day life in torch, clock, toys etc.

12. • Construction:
• Zinc Container acts as cathode i.e. negative electrode while carbon rod
acts as positive electrode or anode.
• It shall be noted that carbon rod is covered with Manganese dioxide and
kept in canvas bag. Here the mixture of coke and Manganese dioxide acts
as depolarizer.
• In Dry Cell, electrolyte solution is paste of sal ammoniac and Zinc Chloride
• Upper portion of cell is covered with saw dust and pitch compound and a
small hole is kept intentionally for venting of cell.

13. • Working:
• When dry cell is externally connected with wire, following reactions take
place,
• Zn + 2NH4 Cl = ZnCl2 + 2NH3 + H2
• Here NH3 and H2 are in the form of ions.
• Ammonia dissolves in water and after saturation it comes out. It shall be
noted here that, H2 reaches to anode i.e. toward the carbon rod and there
it reacts with MnO2 to makes water.
• 2MnO2 + H2 = Mn2O3 + H2O
• Normally the emf of dry cell is 1.5 V . These cells are used in portable
equipment like Transistor, Torch, TV remote, remote bell push etc.

19. Thermal effect of electric current:
• When a current flows through a conductor, heat energy generates in the
conductor. The heating effects of electric current depend on three factors:
• The resistance of the conductor. A higher resistance produces more heat.
• The time for which the current flows. The longer the time the amount of
heat production is high.
• Higher the current the amount of heat generation is also large.

20. • Joule’s law states the amount of heat production in a
conductor is :
• Directly proportional to the square of electric current flowing
through it.
• Is directly proportional to the resistance of the conductor.
• Directly proportional to the time for which electric current
flows through the conductor.
• H = I2Rt. (Joule’s equation)

21. • Application of heating effects of current:
• Electric heater and water heater:
• When these appliances are in connection with the supply of
electricity they become hot but wires remain cold.
• They consist nichrome which has high resistivity and hence
high resistance.
• Heat produced is directly proportional to the resistance of
material through which the current flows.

22. • Electric bulb:
• The filament of an electric bulb consists of tungsten with a
high melting point.
• Since the resistance of thin filament is very high, amount of
heat production is large same as the electric current that
flows through the filament.
• Due to a large amount of heat production, the filament bulb
becomes white hot. Hence filament of bulb emits light and
heat.

23. • Electric fuse:
• A fuse is a safety device which prevents damages to electrical
circuits and possible fires.
• When large electric current flow through a circuit and hence
through fuse wire, a large amount of heat production occurs.
• Due to this large heat production, the fuse wire melts and the
circuit breaks so that the current stops flowing through the
circuit

24. • Electric iron:
• The element of the electric iron constitutes alloys
having a high melting point. Electric heater and
geyser work on the same mechanism.

25. Electrolysis:
• chemical decomposition produced by passing an electric
current through a liquid or solution containing ions.
• the removal of hair roots or small blemishes on the skin by
the application of heat using an electric current

26. • Principle of electrolysis:
• Electrolysis is an electrochemical process by which current
passes from one electrode to another in an ionized solution
that is an electrolyte.
• In this process, positive ions or cations come to the negative
electrode or cathode and negative ions or anions come to the
positive electrode or anode.

27. Electrolytic burn:
• An electrical burn is a burn that results from electricity
passing through the body causing rapid injury.In extreme
cases, electricity can cause shock to the brain, strain to
the heart, and injury to other organs
• Electrical burns differ from thermal or chemical burns in that
they cause much more subdermal damage. They can
exclusively cause surface damage, but more often tissues
deeper underneath the skin have been severely damaged

28. • there are six main types of electrical burns:
• arc burns,
• low voltage burns,
• high voltage burns,
• oral burns, flash burns,
• and flame burns.

29. Gases

31. • Mass analyzer or Mass spectrometry is a powerful analytical
technique used to quantify known materials, to identify
unknown compounds within a sample, and to elucidate the
structure and chemical properties of different molecules.

33. • Thermionic emission is widely used as a source of electrons in
conventional electron tubes (e.g., television picture tubes ,
fluorescent lamps ) in the fields of electronics and
communications.
• Thermionic devices are ,
• Thermionic and Semiconductor Diodes.

34. Diodes
• A diode is a two-terminal electronic
component that conducts current primarily in
one direction; it has low resistance in one
direction, and high resistance in the other.

36. Electronic tubes
• A tube is a device that controls electric current flow in a
high vacuum between electrodes to which an electric
potential difference has been applied.
• The vacuum tube is often used to amplify weak currents or
act as a one-way valve (rectifier) for electric current.
• There are also several uses of electronic tube like in T.V .
• Since Diodes and Triode are also kind of electronic tubes .