This document discusses electric current and its microscopic view. It defines current as the rate of charge flow through a surface and provides the formula and SI unit. It discusses types of charges, when moving charges constitute a current versus when they do not, and the direction of current flow in a conductor. It also addresses how current is measured, how small currents are expressed, and the heating, magnetic, and chemical effects of current. Sample problems are provided on calculating current from charge and time as well as determining drift velocity and current density. The document concludes by distinguishing between direct and alternating current.

1. Urwa Arshad
F2019067084
Electric Current & Microscopic view of electric
current

2. Introduction
 Electric current& formula& S.I. unit& quantity
 Types of charges
 Moving charges is a current or not a current
 Electric current in a conductor
 Direction of electric current
 How electric current measures?
 How Small quantities of electric current are expressed?
 Effects of current
 Sample problem
 Drift velocity
 Current density
 Sample problem
 Types of current

3. Electric current
 Def: The current is the rate at which
charge flows through surface.
 Meaning: flow of electrons
 Iavg=∆Q/∆t
 I ins= dQ/dt
 S. I unit is 1A
 IA=1C/s
 Electric current is a scalar quantity.

4. Types of charge
 There are two
types of charge.
 Positive charge.
 Negative charge.

5. Moving charges as a current or
when moving charges is not
current Its described as a
steam of moving
charges.
 May range very small
currents such as the
nerve impulse to a
large as the solar wind
emitted by the sun.
 There must be a “net”
flow of charges
towards one direction.
 When there is no net
flow of charge even
though there are
actual movement.
 Examples:
 Electrons of a copper
conductor in absence
of electric potential.
 Electrons just move
randomly the charge
flowing to one
direction is equal to
those flowing to the
other direction

6. ELECTRIC CURRENT IN A
CONDUCTOR
Depend upon potential difference
Material in which charges passing

7. Direction of electric current
Movement of
electron along the
conductor.
Electrons are
negatively charged.

8. An instrument
called “ammeter”
measures electric
current in a circuit.
Indicated by capital
letter ‘A’.
Ammeter

9. How small quantities of
electric current are
expressed?
The small quantities of electric current
are expressed in :-
1. Milliampere ( 10 -3A )
2. Microampere ( 10 -6 A)

10. Effects of electric current
1. Heating effect (H=I2RT)
2. Magnetic effect: produces magnetic
field depend on value of current and
distance.
3. Chemical effect: dilute sulphuric aid
and copper sulphate are used as
electrode. Which conduct electricity
due to some chemical reactions.

11. Effects of electric current
Chemical effect Magnetic effect

12. ELECTRIC CURRENT
SAMPLE PROBLEMS
A wire carries a current of 0.2 ampere.
How many electrons passes in 2 s?
When charge is 4microcoloumb and time
is 2 s. What is current?

13. Drift velocity
The net
motion of
charged
particles
as a
group:
I =Q/t
=n(q)vd A

14. CURRENT DENSITY
Current per unit of cross-sectional area of
a conductor.
A vector quantity with the same direction
as the motion of positive charge carriers.

15. SAMPLE PROBLEM
Question no 1
A 491 gauge copper wire has a nominal
diameter of 0.64mm. This wire carries a
constant current of 1.67A to a 4,910 watts
lamp. The density of free electron is
8.5*10*28 electrons/m3.Find the current
density and the magnitude of drift
velocity?

16. Types of current
Direct current: developed by Tomas
Alva Edison.
Graph is straight line.
Alternating current: developed by
Nekoola Tesla and George
Westinghouse, forming revalry with
Thomas Edison on War of the
Currents.
Graph is sinosoid.

17. TYPES OF CURRENT
A. Direct current
B. Alternating current

18. Thank You!