Definition, formula, ohms law, electric power and power usage of appliances

1. ELECTRIC CURRENT
By
Duddu Sampurna Rao, M.Sc.,
Lecturer in Physics,
KRK Govt. Degree College,
Addanki, Prakasam Dist.

2. Topics
• Definition
• Ohms law
• Current Types
• Effect of current on human body
• Calculation of resistance resistors
• Electric Power
• Daily usage Electric instruments

3. Definition
• An electric current is the rate of flow
of electric charge through a point in electric
wire.
• The SI unit of electric current is the ampere,
which is the flow of electric charge across a
surface at the rate of one coulomb per
second.
• Electric current is measured using a device
called an ammeter.

4. Definition(Conti.)

5. Ohms law
• Ohm's law states that the current through a
conductor between two points is
directly proportional to the potential
difference across the two points.
• Introducing the constant of proportionality,
the resistance(R).
R
I
VIV 

6. Ohms law(Conti.)

7. Current Types
• Nowadays two types of Electric currents are
used.
• Alternating current and Direct Current
• Def: An electric current that reverses its
direction many times a second at regular
intervals is called Alternating Current.
• AC is the form of electric power most
commonly delivered to businesses and
residences.

8. Current Types (Conti.)
• The usual waveform of an AC power circuit is
a sine wave.
• Certain applications use different waveforms,
such as triangular or square waves.
• Audio and radio signals carried on electrical
wires are also examples of alternating current.
• An important goal in these applications is
recovery of information encoded
(or modulated) onto the AC signal.

9. Current Types (Conti.)
• In contrast, direct current (DC) is the unidirectional
flow of electric charge, or a system in which the
movement of electric charge is in one direction only.
• Direct current is produced by sources such
as batteries, thermocouples, solar cells,
and commutator-type electric machines of
the dynamo type.
• Direct current may flow in a conductor such as a
wire but can also flows
through semiconductors, insulators, or even through
a vacuum as in electron or ion beams.
• An old name for direct current was galvanic current.

10. Current Types (Conti.)

11. Resistance of human body

12. Effect of current on human body

13. Effect of high voltage lines on birds

14. Electric Power
• Electric power is the rate(per unit time) at
which electrical energy is transferred by
an electric circuit.
• The SI unit of power is the watt or one joule
per second.
• Electric power is usually produced
by electric generators, but can also be
supplied by sources such
as electric batteries.

15. Electric Power(Conti.)
• It is usually supplied to businesses and
homes (as domestic mains electricity) by
the electric power industry through
an electric power grid.
• Electric power can be delivered over long
distances by transmission lines and used for
applications such as motion, light or heat
with high efficiency.

16. Electric Power(Conti.)

17. Electric Power(Conti.)

18. Electric Power(Conti.)

19. Thank you