This lectures delivers the effects of current on materials. Heating effect, Lightening current, chemical effects, types of cells, types of batteries, series and parallel connections of cells

1. Duration: 60 min DPT Medical Physics Lecture 04
Effects of Current
Instructor:
Engr. Taimoor Muzaffar Gondal
taimoor.muzaffar@superior.edu.pk
Lecture 04

2. Duration: 60 min DPT Medical Physics Lecture 04
Thermal Effect of Current
Wire heats up as a current passes through it
Electrical energy is converted into heat energy
Heat produced depends on the resistance of the
wire
Greater resistance, greater heat
Heating appliances have coils of wires made of
high resistance materials such as nichrome
Heating elements heat up when current passes
through them
Heat produced is then used for ironing, toasting,
cooking and drying

3. Duration: 60 min DPT Medical Physics Lecture 04
Magnetic Effect of a Current
 An iron rod placed inside a coil of wire has increased magnetic field when
the current is switched on
 When the current is switched off, the iron loses its magnetism
 The set-up is known as an electromagnet
 Used in many applications
 Gives a magnetic field that can be switched on and off. when desired

4. Duration: 60 min DPT Medical Physics Lecture 04
Applications of the Magnetic
Effect of Current
Giant electromagnet
Telephone
Electric motors

5. Duration: 60 min DPT Medical Physics Lecture 04
 Liquids such as salt water, vinegar and copper sulphate solution allow
electricity to pass through them
 Liquids are known as electrolytes
 An electrolyte is a substance that produces an electrically conducting
solution when dissolved in a polar solvent, such as water.
 Electrolysis: Chemical decomposition of an electrolyte by an electrical
current
 Electrodes: Two wires or plates through which current enters and leaves the
electrolyte
Chemical Effect of a Current

6. Duration: 60 min DPT Medical Physics Lecture 04
Application of the Chemical
Effect of Current
 Electrolysis is used in electroplating
 Flow of current causes a thin layer of metal to be deposited on the
object to be electroplated
 Electrolysis is also used in industries to extract metals such as
aluminium and magnesium from their compounds

7. Duration: 60 min DPT Medical Physics Lecture 04
Applications of Electroplating

8. Duration: 60 min DPT Medical Physics Lecture 04
Lighting Effect of a Current
 Heating effect of a current can also lead to the lighting effect
 In a light bulb, the heat generated is so great that the coiled
filament begins to glow and give out light

9. Duration: 60 min DPT Medical Physics Lecture 04
Introduction to Batteries
 Batteries consist of two or more voltaic cells that are
connected in series to provide a steady dc voltage at
the battery’s output terminals.
 The voltage is produced by a chemical reaction inside
the cell. Electrodes are immersed in an electrolyte,
which forces the electric charge to separate in the
form of ions and free electrons.
Batteries:

10. Duration: 60 min DPT Medical Physics Lecture 04
The Voltaic Cell
 A voltaic cell consists of two different metal electrodes that
are immersed in an electrolyte (an acid or a base).
 The chemical reaction resulting from the immersion produces
a separation of charges.
 The current capacity increases with large electrode sizes.
 The negative terminal is considered the anode of the cell
because it forms positive ions in the electrolyte. The opposite
terminal of the cell is its cathode.
 Motion of electrons in ionic bonding can be used to generate
an electric current
 A device constructed to do just this is called a voltaic cell, or
cell for short

11. Duration: 60 min DPT Medical Physics Lecture 04
Type of Cells
 Whether a battery may be recharged or not depends
on the cells used to make up the battery.
 A primary cell cannot be recharged because the
internal chemical reaction cannot be restored.
 A secondary cell, or storage cell, can be recharged
because its chemical reaction is reversible.
 Dry cells have a moist electrolyte that cannot be
spilled.
 Sealed rechargeable cells are secondary cells that
contain a sealed electrolyte that cannot be refilled.

12. Duration: 60 min DPT Medical Physics Lecture 04
There are several different types of primary cells in use today:
Carbon-zinc dry cells.
Alkaline cells.
Zinc chloride cells.
Mercury cells.
Silver oxide cells.
Types of Primary Cells

13. Duration: 60 min DPT Medical Physics Lecture 04
Carbon-Zinc Dry Cell
 This is one of the most popular
primary cells .
 The negative electrode is made of zinc.
 The positive electrode is made of
carbon.
 The output voltage of a single cell is
about 1.5 V.
 Performance of the cell is better with
intermittent operation.

14. Duration: 60 min DPT Medical Physics Lecture 04
Alkaline Cells
 The alkaline cell is another popular type also used for type AA, C, D, etc.
 It has the same 1.5V output as carbon-zinc cells, but they are longer-lasting.
 It consists of a zinc anode and manganese dioxide cathode in an alkaline electrolyte
(potassium hydroxide).
 It works with high efficiency even with continuous use, due to low internal
resistance.
Zinc Chloride Cells
 This cell is also referred to as a “heavy-duty” type battery.
 It is a modified zinc-carbon cell.
 It has little chance of liquid leakage because the cell consumes water along with the
chemically active materials. The cell is usually dry at the end of its useful life.

15. Duration: 60 min DPT Medical Physics Lecture 04
Series and
Parallel
Connections
of Cells

16. Duration: 60 min DPT Medical Physics Lecture 04
End of Lecture 04
For any kind of queries and questions you are advised to
write at
taimoor.muzaffar@superior.edu.pk
Or visit my office during consulting hours
This lectures can also be downloaded from
https://www.slideshare.net/Taimoor_Gondal