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Electricity

-

it

is

a

property

of matter

that

results from

the

presence

or movement of

electric

charge. According

to

modern

theory,

matter is electrical

in nature.

ELECTRICIW

o

Basic Data About

the Atom

.

Proton

-

it is a

positively

charged

particle

.

Electrcn

-

it is negatively

charged

particle.

.

Neutron

-

is a

particle

with

neutral charge

(no

charge)

-

Atomic Number

-

it

represents

the

number

of

protons

or electrons

of

an

atom

-

Atomic

Mass

-

it represents

the,sum

of

protons

and electrons

of

an

atom

-

lon

-

it

is an atom

gr

a

group

of

atoms

that

has

a net

positive

or

negative charge resulting

from

unequal number

of

positively

charged

protons

and negatively

charged

electrons,

-

Shell

-

it

is

an

energy level

or

region about the nucleus of

an

atom

in

which electrons

move, The atom has 5

shells,

namely, the

K-shell

(first

orbit), the

L-shell

(second

orbit), the

M-shell

(third

orbit), the

N-shell

(founh

orbit)

and the

O-shell

(fifth

orbit)

-

Valence

electrons

-

is the electrons found in the outermost

shell

(valence

shell) or

orbit

of an atom.

1112612014

THE

ATOM

THE

ATOM

(cont...)

1.602

x

10-21

C,

negative

1.672 x

70

27

kg

.

Electrical

conductors

-

these

are

materials

that

allow the

essentially

free

passage

of

current

when

connected

to

a

battery or

other

source

of

electrical

energy.

(e.9.

copper-29

& aluminum-13)

.

Electrical lnsulators

-

these are materials that

posses

low

conductivity or offer

a

relatively

high resistance

to the flow

of electric current.

They are

also called as

dielectrics.

(e.g

phosporus-15)

.

Electric

Semiconductors

-

these

are

materials

that

have

conductivity about midway between

good

conductors

and

good

insulators

(e.g germanium-32)

ETECTRICAT CTASSIFICATION

OF

MATERIALS

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Elect,ia Current

(l)

-

it

is

the motion or tEnsfer

of charges

from one

region

of

a

condudor

to

another lts unit is the Ampere

(A)

named after And16

Marie Ampare

(1775-

1836)

i

=

dQ/dt

Where:

t

=

time which the current

flowsthrou8h

a material

1 c=6,28

x

1010 electrons

ELECTR CAL

TERMINOLOG ES

Electric

Voltage

(V

or

E)

-

it

as

the work done in moving

a

unit charge

(+1

C)

thrcu8h

an

element

from one termihal to the other lt is al$ called

as

electric

potential

or

electromotive

force

(emf)

lts

unit

is

the

Volt

(V)

named

in

honor

of

the

ltalian

Phvsicist Alessandro

Guissepe Antonio Anadacio Volta

(1745

-

1827), the inventor

of

the voltaic batery

Elect.ic

Resistance

lR)

-

it isthe

prcperty

ofa

material that limits the ahount

offlow

of current and

converts electric energy

to

heat energy. lts unit is the Ohm

(o)

named

in honor ofthe German

Physicist Geor8 Simon Ohm

(1787

-

1854)

OHM'S IAW

According to

Ohm's

Law'At

steady-state

condition, the

voltage ac.oss

a

resistor

is

directly

p.oportlonal

to

the current flowinB

through

it with th temperature remaining

constant."

11t26t2014

lv:'RE

l"=i.H

[';iE

Electrical Power

(P)

-

it

is

defined

as

the

rate

at

which electrical energy

is

expended

or

used up.

It is

the rate electric energy is

converted

into

another

form,

such as

light,

heat or

mechanical

energy

(or

converted

from

another

form

into

electrical

energy). lts unit is the

Watt

(wl

named

after the

Scottish

Engineer lames Watt

(1736

-

1819).

where:

V

=

applied

voltage in

volts

Georg Simon Ohm

I

=currentdEwninamperes

(797-1g'll

R

=

resistance in ohms

ELf,CTRICAL

POWER

mmmm

P

=

electrical

power

in watt

Note:

V

=

voltage in

volt

1

HP)

=

746 w

I

=currentinamper"a

I

=looow

R

=

resistance in ohm

I w)= 1'ooo'ooow

James

Watt

Electric

Circuit

-

it is a collection

of

electrical

elements

interconnected

in

some

specific way through

which

electric current

flows or it

is intended to flow.

ELECTRIC CIRCUIT

Eleclrlc

Glrcults

A

circuit consists

of

a

source, conducting

parts

and a load,

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WPES OF CIRCUIT CONNECTIONS

1.

Series

circuit

2. Parallel circult

3. CombinationalCircuit

a.

Series-parallel circuit

-

it is a combinational circuit

when simplified

will result into a series circuit

b.

Parallel-series

circuit

-

it is a combinational

circuit

when

simplified

wlll result into a

parallel

circuit.

1. se.ies

Grcuit

-

the

circuit elements are

lFl

t ,

said to

be

connected

in

serietwhen they

|

't

-I--

L

+

"

all carry

the same

cur.ent.

I

,,

ln,

2. Propedieiofaseriescircuit:

I r Sr

),

The same current

.flows

through

all

the

,,

I

+t

l''

esistan.es. V,

':

1

->'

)

There

will

be voltage drop

across

each F

v?

=

R'?

resi(ance. I fll,.

;

The sum

of

the

voltege drops is equal to

I

-J-

-

t

theappliedvoltage.

I

v.2n.

3.

EquivalentResistance

of

a Series

Circuit: I r

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1.

The

equivalent resistance of

four resistors

joined

in

parallel

is

20 ohms.

The

currents flowing through

them

are

0.6, 0.3, 0.2 and 0.1 ampere.

Find

the

value

of each

resistor.

2. Two bulbs

of

250 W, 230 V each, are connected across

a

200

V

supply. Calculate

the total

power

drawn from

the

supply.

3.

Two resistances,

one

of 30 ohms and another of unknown

value are

connected

in

parallel,

the total

power

dissipated

in

the circuit

is 450

watts when

the

applied

voltage is

90

volts. Find the

value

of the unknown

resistance.

Sample

Problems

Voltage Divider Circuit

-

it is a

series

circuit which

is used

to

feed

other

networks

with

a

number of

different

voltages and derived from

a single

lnput voltage source,

lt

also

called as

a

potential

divlde..

VOTTAGE DIVIDER THEOREM

11t26t2014

Current

division

-

it

refers

to the

spliting of current

between

the

branches of the

divider

The

currents

in

the various branches

of

such

a

circuit

will

always divide in

such a way as

to

minimize

the

total

energy

expended.

CURRENT DIVIDER

THEOREM

t[ffi--*

I / R, \N

'.'-,'1n;tcl

$

l s f fi

r--;-;.-i-E

1,,=+(6;6J

fr

t.*".-*....^-N

4