Transcript Electricity - CURENT Education

1
Introduction
Current Electricity
Moving charges/electrons
Current electricity is controlled movement of
charges through a path, usually a conductor
of electricity.
Difference between static and current electricity
Examples of static electricity:
Examples of current Electricity:
Lightning- static or current?
Measuring Electricity
Parameter
Definition
Units
Current
Flow of
electrons
Ampere (A) I
Ammeter
Voltage
Potential
difference
Volts
(V)
V
Voltmeter
Resistance
Opposing
force to
current
Ohms
(Ω)
R
Ohmmeter
Power
Energy
used in 1
sec
Watts (W)
Joule/sec
P
Wattmeter
Energy
Joules
Watt-hour
Symbol
Measuring
meter
4
Circuits
Objectives: To understand
Components of a circuit
Electrical circuit, an electrical network that
has a closed loop giving a return path for
the current.
Usually consists of source(pusher),
path(conductor) and load(user)
Components of Electric circuit
Circuit
component
Definition
Examples
Electric Source
Source of electric energy/current
Battery, Solar cell,
Electric generator,
Electric Load
anything that uses/absorbs the
energy that is being delivered by
the electric current in a circuit
Lamps, fan, washing
machine, computer,
Resistance
Switches
A device that connect circuit
/allow flow of electrons when
“on”
Electronic switches,
Mechanical switch
Measure current, voltage and
power
Ammeter,
Voltmeter,
wattmeter
Measuring
devices
5
6
Symbols(review)
the Ammeter
Voltmeter
resistor
Switch
battery
Light bulb
▫ Light bulb
7
Activity
1) Collect your
activity packet
2) Learn how to use
multimeter.
• All measuments
only DC in this
class
• Only milli Ampere
of current
measured
8
Multimeter
How to connect probes
▫ Connect red probe into “VΩmA” slot
▫ Connect the black probe into
“COM”
How to set the dial to measure the
right quantity
▫ To measure voltage,
▫ current and
▫ resistance
Resistance
Voltage
What scale to choose?
9
Activity 1: Voltage
1) Measure voltage of batteries
a) AA
b)AAA
c)D
d)9V
2) Swap the connections. What is the voltage?
3)Connect two batteries in series
▫ What is the voltage?
4)Swap one of the batteries at terminals
▫ What is the voltage?
10
Series
▫ Connect resistors in series.
Parallel
Voltages in parallel
Resistors in parallel
11
Voltage and Current
Measure current for 1.5V, 100 ohms.
Measure current for 1.5V, 1000 ohms.
Voltage(V)
Resistance(
R)
1.5V
100 ohms
1.5V
1000ohms
Current (I)
Relation
between V
and I
12
Ohm’s law
Ohm’s law relates the relation between
voltage and current.
As voltage(V) increases, current(I) increases
V=I*R
where V is emf/ voltage, I is current, R is resistance
emf is electromotive force
Assumptions:
Only for conductors, resistors called “ohmic materials”
Materials that do not obey Ohm’s law are called
“non-ohmic” materials
13
Power and Energy
Electric Power is measured in Watts
Electric Energy is measured in Watts-hr.
1 watt-sec= Joule
Electric power = voltage × current, or
P=V×I