2. Presentation on PHYSICS - II
Lecturer
Shalauddin
Department of General Education Development (GED)
Daffodil International University , Bangladesh
PRESENTATED BY :
Khokan Chandra Biswas
PRESENTATED TO:
5. What is Electricity ?
Electricity is a form of energy that can be easily changed to
other forms.
Why does electricity come from?
Electricity come from mainly two source:
Electricity
Power station Electrical cells
7. Electric Charge
What is electric charge?
Electric charge is the physical property of matter that causes it to
experience a force when placed in an electromagnetie field.
Units for Electric Charge:
*The symbol for electric charge is usually a “q”.
*The SI derived unit of electric charge is the coulomb(C).
Example:
8. There are two kind of charge:
*positive Charge.
* Negative Charge.
Basic Properties of Electric Charge :
1.Additive Nature :
Charges add up like real numbers.
Example:
A system of 3 charges q1,q2 and q3
Q(n) =q1+q2+q3
Let q1=3c,q2=-2c and q3=6c
Q(n) =(+3)+(-2)+(6)=7c
9. 2.Conservation of Charge:
Total charges of an isolated system is always conserved.
Example:
Change particles may be created or destroyed. but charge can
not created or destroyed.
3.Quantization of charge:
All free charge are integral multiple of a basic unit of charge
denoted by e.
Q(any body)=ne
Where n=any integer.
Q1+Q2=Q3+Q4
Accroding to the above law
10. Why all object are charged?
All object are matter ,which is composed of atoms.Every atoms
has the potential to charge is electronic composition by adding
or substracting electrons ,which induced a negative or positive
charge.
*pollution controllers
*Smokestacks
*Air freshners
*Xerography
*Painting cars
Application of Charge:
11. Electric Current
What is electric Current?
An electrical current is the rate of flow of electric charges in a
circuit.
Units for Electric Charge:
The SI unit of current is the ampere ; one ampere is defined to
be one coulomb per second(1A=1C/S).
Type of Current:
1.Direct current
*The direction of current is constant.
*The graph of current vs time is a straight line.
12. 2.Alternative current
*The direction and magnitude of the
current .Continuously charges
between two extremes.
*The graph of current vs time is
sinusoid.
Electric Resistance
Resistance is the opposition that an electrical device has to the
flow electrical current.
It denoted as R and its unit is ohm.
Figure 1
13. Resistivity
Specific electrical resistance quantifies how strongly a
given material opposes the flow of electric current.
Mathematically:
R=PL/A
Where,
R=Resistance (ohm)
P=Resistivity
L=Length of the wire ( m)
A=cross-sectional area of a wire (m2)
14. Conductivity
Electrical conductivity is the reciprocal of electrical resistivity
,and measures a materials ability to conduct an electric current.
It is represented by Greek letter sigma but K(kappa0 Or
gamma are also used.
Its SI unit is simens per meter(s/m)
15. Electric Circuit
An electric circuit is a conducting path , extermal to the battery
,which allows charge to flow from one terminal to other.
Ohms law
The current through a conductor between two point is directly
proportional to the voltage across the two points .
Mathematically:
V=IR
16. There are two kind of electric circuit:
1.Series Circuit
2.Parallel circuit
1.Series Circuit
*A series circuit connects the components one after the other
*A single loop is formed
*A break in any part of a series circuit stops the flow of
currents the whole circuit.
17. 2.Parallel Circuit
*A parallel circuit divides into two or more branches.
*The current divides and flows through each parallel branch
*If a component breaks or is removed, the components remain
on.
