2. What is ELECTRICITY?
Electricity is a form of energy that can
be easily changed to other forms,
resulting from the existence of charged
particles (such as electrons or protons).
3. Electricity
is generated with steam turbines
using fossil fuels, nuclear, biomass,
geothermal, and solar thermal
energy. Other major electricity
generation technologies include gas
turbines, hydro turbines, wind
turbines, and solar panels.
4.
5. Michael Faraday - The Father of Electricity
He was born on September 22, 1971, was an
English scientist who contributed to the fields of
electromagnetism and electrochemistry. His main
discoveries include those of electromagnetic
induction, diamagnetism and electrolysis.
6. How to make an electric appliance
work?
To make an electric appliance work,
electricity must flow through it.
The flow of electricity is called an electric
current.
The path along which the electric current
flows is called the electrical circuit.
7.
8. What is Electric Current?
- Current is the rate of flow of
electrons/charge
- It is abbreviated as I
- It is measured in amperes
- One ampere is defined as one coulomb of
electrons flowing past a point each
second (Q/s)
9. Electric Charges
• Electric charges are made up of positive charges
(protons) and negative charges (electrons).
• When these charges flow in a circuit, a current
is produced.
10. How does electricity flow?
• The battery in a circuit gives energy to the
electrons and pushes them around a circuit,
from the negative terminal of the cell, round
the circuit and back to the positive terminal of
the cell.
11. • The SI unit for electric current is
ampere (A).
• Smaller currents are
measured in milliamperes
(mA).
How to Measure Current?
1 A = 1,000 mA
1 mA = 0.001 A
12. Instrument to Measure Current
• An ammeter is an instrument used for
measuring electric current, connected in
series in the circuit.
A
13. Positive side of ammeter must be
connected nearest to the positive
terminal of the battery (electric cell),
and vice versa.
14.
15. VOLTAGE
- Voltage is a force that pushes the electrons/
charge
- It is also referred to as electromotive force or
difference in potential, abbreviated as E or EMF
- Voltage source will have a polarity (negative and
positive side) Current flows from negative to
positive (changing conventions) AC/DC.
- Alternating current (polarity of source reverses)
or Direct current (polarity is constant)
16. Voltage
• An electric cell gives energy to the electrons and
pushes them round a circuit. Voltage is a measure of
how much energy the electrons receive.
• Different voltages are supplied by different cells and
batteries.
12 V Car Battery
1.5 V
Dry Cell
9 V
Dry Cell
17. How to Measure Voltage?
• The SI unit for voltage is volt (V).
• A voltmeter is an instrument
used for measuring voltages.
V
18. Different cells produce different voltages.
The bigger the voltage supplied by the cell,
the bigger the current.
Unlike an ammeter a voltmeter is
connected across the components
Scientist usually use the term Potential
Difference (pd) when they talk about
voltage.
19.
20. • When an electric current flows
through a circuit, there will be some
resistance that opposes it. It is
abbreviated as R It is measured in
ohms.
21. • Good conductors of electricity have
LOW RESISTANCE.
• Poor conductors of electricity have
HIGH RESISTANCE.
22.
23.
24. It is a closed path along
which electron can flow
from and return to an
energy source.
25. Here is a simple electric circuit.
It has a cell, a lamp and a switch.
cell
switch
wires
lamp
To make the circuit, these components are connected
together with metal connecting wires.
26. The CELL stores chemical energy
and transfers it to electrical
energy when a circuit is
connected. When two or more
cells are connected together we
call this a Battery. The cells
chemical energy is used up
pushing a current round a circuit.
27. In simple circuit, when the switch is closed,
the lamp lights up. This is because there is
a continuous path of metal for the electric
current to flow around. If there were any
breaks in the circuit, the current could not
flow.
29. circuit diagrams
In circuit diagrams components are represented by the
following symbols;
cell battery switch lamp buzzer
ammeter voltmeter motor resistor variable
resistor
31. 2 Types of Circuit
Series Circuit Parallel
Circuit
32. SERIES CIRCUITS
The components are connected end-to-end, one after the
other.
They make a simple loop for the current to flow round.
If one bulb ‘blows’ it breaks the whole circuit and all the
bulbs go out.
33. PARALLEL CIRCUITS
The components are connected side by side.
The current has a choice of routes.
If one bulb ‘blows’ there is still be a complete circuit
to the other bulb so it stays alight.
34. Measuring current
This is how we draw an ammeter in a circuit.
Electric current is measured in amps (A) using an ammeter
connected in series in the circuit
A A
Series Circuit
Parallel Circuit
A
35. Measuring Current
SERIES CIRCUIT
• current is the same
at all points in the
circuit.
PARALLEL CIRCUIT
• current is shared
between the
components
2A
1A
1A
2A 2A
1A
2A
2A
36. copy the following circuits and fill in the
missing ammeter readings.
4A
?
?
3?
3A 3A
?
?
?
41. Measuring Current & Voltage
Copy the following circuits on the next two
slides.
Complete the missing current and voltage
readings.
Remember the rules for current and voltage
in series and parallel circuits.
