3. *An electrical property of
matter that exists because
of an excess or deficiency of
electrons
*Symbolized by Q
*A force acts between
charges
*This force, called an
electric field, consists of
invisible lines of force
Figure 2: Force between Charges
Figure 3: Electric field between two
oppositely charged surface
3
4. *Q is measured in coulomb, C
*1 C = 6.25 x 1018 electrons
*1 electron = 1.6 x 10-19 C
*The total charge, Q, expressed in coulombs, for a given number
of electrons is stated in the following formula:
Ce
electronofnumber
Q
/1025.6 18
4
5. *The amount of energy per charge available to move electrons
from one point to another in an electric circuit.
*The formula for voltage is:
*One volt is the potential difference (voltage) between two
points when one joule of energy is used to move one coulomb of
charge from one point to another
Q
W
V
Voltage (unit: volt, V)
Work (unit: joules, J)
Charge (unit: coulombs, C)
5
7. • Voltage is like differential pressure,
always measure between two points.
• Measure voltage between two points
or across a component in a circuit.
• When measuring DC voltage make
sure polarity of meter is correct,
positive (+) red, negative (-) black.
7
Figure 4: Voltmeter
8. *
*Uniform flow of electrons
thru a circuit, is called
Current
*Symbolized by I
*Formula:
t
Q
I
Current
(unit: Ampere, A) Time
(unit: second, s)
Charge
(unit:
Coulomb, C)
Figure 5: Illustration of charge
Figure 6: Illustration of 1 A of current
(1 C/s) in a material
8
9. *2 types of current
*Direct current (DC)
*A current that remains
constant with time
*Alternating current (AC)
*a current that varies
sinusoidally with time
(a)
(b)
Figure 7: Flow notation of (a) electron
(b) conventional
WILL USE CONVENTIONAL FLOW NOTATION
ON ALL SCHEMATICS
Figure 8 (a): Direct current
Figure 8 (b): Alternating current9Pn Shareen Adlina
10. 10
Voltmeter – MEASURE VOLTAGE
AMMETER – MEASURE CURRENT
OHMMETER – MEASURE RESISTANCE
MULTIMETER – MEASURE VOLTAGE,CURRENT AND RESISTANCE
Analog meter
Digital multimeter
