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Alternating Current

Direct Current

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Components of Electrical System

Voltage = term used to designate electrical pressure or force that causes

current to flow

Voltage source = generator/batteries

Conductor = wires

Control Element = switch

Load = light bulb, motors, appliances

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Direct Current (DC)

The first type of current because it was easy

to produce.

Type of current always flows in one direction

One of the disadvantages of using DC is theexcessive voltage drop and power loss in the

power lines in a long distance transmission.

Example: battery

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Alternating Current (AC)

s the solution to the problem of DC

Allows the flow of current in two directions

T!A"#$O!%E! & is the device used for

stepping'up or stepping'down AC voltage#tep'up to a power station( transmit it to any

distant place and step it down to for consumption

#ource: AC outlet ) **+ volts

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AC vs. DC

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O,%-# A/ A"D 0O/E!

A/

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O,%-# A/

#tates that: for a steady current1

the current in a circuit is directlproportional to the total E%$

acting in the circuit and in!erselproportional to the totalresistance of the circuit.

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O,%-# A/

The law may be expressed by the

following e2uation:

f the current I is in amperes

the electromotive force V is in volts

!esistance R is in ohms

Discovered by "eorg #imon $hm

3

! )

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#ample 0roblem 4:

/hat is the potential difference in an

electric circuit with a current of 45

amperes and a resistance of 6.+ ohms7

8iven: ) 45 A( ! ) 6.+ 9 $ind:3 ) 7

#ol-n: ) 3!( 3 ) ! 3 ) 45 A x 6.+ 9 );+ 3

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#ample problem *:

/hen a 4*'volt automobile battery is

connected across a resistor of un

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Exercise 4:

Estimate the resistance of the following

common household appliances1 assuming a

voltage of 4*+ 3 is applied across them:

a. A hair blower that has a current of 4+ A(

b. A >+'watt 3C! that carries a current of +.*5 A(

c. A corded electric ra?or that carries a current

of +.4+ A

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Exercise *:

,ow much current is drawn

from a 4*'volt battery when

a 45'ohm resistor isconnected across its

terminal7

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Exercise >:

/hat voltage must a

battery have to produce

+.5+ A of current througha *.+'ohm resistor7

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#eries and 0arallel

Circuits

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!esistance in #eries

Allow current to flow through one single path

#can page >@> physics boo@5 physics boo. The reciprocal of the total resistance or e2uivalent resistance in a parallel circuit

is e2ual to the sum of the reciprocals of the separate resistances.IT= I

1+ I

2+ I

3+ + I

N

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EECT!CA #B%O#

Wire

Switch

Lamp

Load

Battery

AC power

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