Electric current is the flow of electrons, with the standard unit being the ampere which is defined as one coulomb of charge passing per second. Current can be either steady direct current (DC), where the magnitude does not change over time as provided by batteries, or alternating current (AC) where the direction periodically changes due to the alternating polarity of the voltage source. Common applications of DC include cell phones and flashlights, while AC applications include appliances, electric motors, and power from wall outlets which is converted to DC for battery operated devices using transformers, diodes, and capacitors.

1. CURRENT

2. DEFENITION
• Electric current is a flow of ELECTRONS. i.e., Charge
• It is a flow of electric charge across a surface at a rate
of 1 Coulomb per second.
• Current flows actually in the opposite direction of
electrons.

3. UNIT
• Current is denoted by the letter I
• SI Unit is AMPERE named after Andre-Marie ampere
• 1 AMPERE=6.24 X 1018 e

4. CALCULATION
• 1 Ampere = 1 Coulomb / Second
Charge on 1 electron = 1.6 x 10-19 Coulomb
• By unitary method,
If 1.6 x 10^-19 Coulomb / Second (Ampere) = Current by 1
electron
then, 1 Coulomb / Second (Ampere) = 1 / (1.6 x 10^-19)
electrons
i.e, 6.24 x 10^18 electrons.

5. CURRENT MEASUREMENT
• Current is measured through the instrument named
AMMETER.
• CURRENT=CHARGE / TIME. i.e. ,Q / T
where
Q - CHARGE
T-TIME
Ancient AMMETER

6. CLASSIFICATION OF CURRENT
The Electric current may be classified into 2 main classes.
(I) Steady Current(DC)
(III) Alternating Current(AC)

7. STEADY CURRENT
When the magnitude of current does not change with
time ,it is called a Steady Current.
The current provided by a battery is almost a steady
current.

8. APPLICATIONS OF STEADY CURRENT
Cell phones
Flash lights
Hybrid and electric vehicles
Etc…

9. ALTERNATING CURRENT
Flow of charges that changes direction periodically
Accomplished by alternating the polarity of the
voltage sources

10. APPLICATIONS OF ALTERNATING CURRENT
Dish washers
Refrigerators
Home appliances
Electric motors
Etc…

11. DIRECT CURRENT VS ALTERNATING
CURRENT

13. DIRECT CURRENT ALTERNATING CURRENT

14. GRAPHICAL REPRESENTATION

15. CONVERTING AC TO DC
• Wall outlets : AC
• Battery operated devices : DC
• AC ADAPTORS have 3 main components:
1. TRANSFORMER
2. DIODE
3. CAPACITOR

16. APPLICATIONS