Notesale: Turn your study into money

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CURRENT ELECTRICITY

What are the sources of electricity?
• Main electricity
• Electric cells
• So what’s the difference?

Main Electricity
• Generated by power stations
• Delivered to homes and industries through
wires
• Finally connected to main sockets
• Supplies a lot of electrical energy

Electric Cells
• Used in many portable electrical devices
• Supplies small amount of energy
• Safe to touch

Electric Current and Circuit
• The rate of flow of electric charges is called electric
current
• Electric circuit is the path which the electric current
takes
...

• When switch is off, the circuit is
opened and the bulb will not light up
• When switch is on, the circuit is closed
and the bulb will light up

Electric Current
• Flow of electric charges or flow of
electrons through a conductor
• depends on # of e- passing a point
in a given time
• measured in amperes (A)

Measuring Electric Current
• Ammeter
SI unit for electric current is ampere (A)
1A = 1000 mA
1mA = 0
...
5V

9V

• Resistance

C
...


Ohm’s Law
• Ohm’s Law

V=I×R

V: potential
difference (V)
I: current (A)
R: resistance ()

• Voltage increases when current increases
...


 A light bulb with Ohm’s Law 160 
E
...
What
is the current flowing through the
bulb?
GIVEN:

WORK:

R = 160 
V = 120 V
I=?
V

I=V÷R
I = (120 V) ÷ (160 )
I = 0
...
Ohm’s Law
electric circuit with a current of 15 A
and a resistance of 4
...
0 
I= 15 A
V=?

V=IR
V = (15 A) (4
...
Ohm’s Sofia’s
toaster uses a 220 V line and draws
2
...
What is the resistance
of the oven when it is fully heated?
GIVEN:

WORK:

I= 2
...
5 A
R= 88 

V

I R

 Rachel gets her calculator to do her
E
...
In the calculator, a
0
...
15 C
t = 2s
R = 18 

WORK:

How circuit can be arranged?
• Series circuit
• Parallel circuit

• The three light bulbs are
Series Circuit
arranged in series
• Each component is joined one
after the other to form a single
path
• Current flows through each
component is the same

• If one bulb in aSeries Circuit
series circuit is removed or
broken, no current flows
• The remaining bulbs do not light up
• Because the circuit is opened

• Any amount of light bulbs are
Parallel Circuit
arranged in parallels
• Divides two or more branches
and has electrical components in
each branch

• The current from the battery divides
Parallel Circuit
and flows through each branch
• If one bulb breaks or removed, other
bulbs on the circuit remain lit
• It is because the circuit remains
closed

What is a resistor?
• Appliances need to ensure that
the correct size of current flows
to operate properly
• To control the size of the
current, electrical components
called resistors are used in the
circuits
...
Find the total
or equivalent resistance
...
Compute the total current
...

GIVEN:

R1 = 6 
R2= 12 
VT= 6 V

WORK:

 A 12
...
Find the total or equivalent
resistance, total current, and the voltages
across each resistor in the circuit
...
0V

WORK:

 A 12
...
Find the total or equivalent
resistance, total current, and the voltages
across each resistor in the circuit
...
0V

WORK:

Mnemonics

Bill Brown Realized Only Yesterday Goo
d Boys Value Good Work

Black Bugs Race Over Yellow Grass,
Beside Violent Grey Water

Sample Problems:
Suppose that you have five appliances
connected in series
...
If the
circuit is connected to a direct current
of 220 V, what is
a
...
the total current?
c
...
The refrigerator
has a resistance of 20 Ω; the TV set, 10
Ω; the radio, 5 Ω; the flat iron, 75 Ω;
and the electric stove, 55 Ω
...
totat resistance in the circuit?
b
...
the voltage across each appliance?



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