CHAPTER 3

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELEMENT AND ELECTRICAL CIRCUIT

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELEMENT/ELECTRICAL CURRENT SOURCE

In daily life, electrical current known as electrical cell or electrical element.

Battery and accumulator is a kind of electrical cell that mostly used in daily life.

There are some kinds of electrical cell such as voltaic element, battery, accumulator, and Weston cell.

Based on the possibility to refill, these elements divided into two groups, namely primary cell and secondary cell.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELEMENT/ELECTRICAL CURRENT SOURCE

1. PRIMARY ELEMENTprimary element is an electrical current source. Primary element is used only once. VOLTAIC ELEMEN

voltaic cell is a current source that is firstly found by Alessandro Volta.

THE WEAKNESS OF VOLTAIC ELEMENTelectrical current that flows can not occur in long time and the potential difference of the poles is low, only ± l volt.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELEMENT/ELECTRICAL CURRENT SOURCE

solution of Sulfate acid

Plate of zinc

Bar of Copper

+-

Voltaic element consists of components :

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELEMENT/ELECTRICAL CURRENT SOURCE

Potential difference = 1,5 V

Dry element ( battery )

Positive poleAmmonium

chloride compound

Carbon bar

place made of

zinc

Negative pole

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELEMENT/ELECTRICAL CURRENT SOURCE

1. Secondary element ( refillable ) Accumulator

Parts of accumulator

arbiter

Sulfate acid

plate of lead

Cell connecto

rcell

container

Cell part

Up shutter

Whole shutter

Positive pole

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELEMENT/ELECTRICAL CURRENT SOURCE

The tool measure electrical-current is voltmeter .

Voltmeter is set parallel to the component which its potential difference will be measured.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELEMENT/ELECTRICAL CURRENT SOURCE

To measure electrical current and potential difference

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELECTRICAL-CURRENT CIRCUIT

a) Non-forked electrical current, the current that flows in the circuit is not forked anywhere, and they are equal.

b) Forked electrical-current, the current that flows in is equal to the current that flow out. The statement known as first Kirchhoff Laws.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELECTRICAL CURRENT CIRCUIT

Electrical current based on its form :

a.Series circuitIt is the set of electrical

components in line. b. Parallel circuit

It is a set of electrical components in alignment.

PHYSICS FOR JUNIOR HIGH SCHOOL IX

ELECTRICAL CURRENT CIRCUIT

3. Ohm Laws in electrical circuit

A scientist from Germany named George Simon Ohm (1789 –1854) had discovered the relation between potential difference and current, then known as Ohm laws. “ current that flows in a conductor is proportional to potential difference among the edge of those conductors (as long as the temperature of conductor is constant).

PHYSICS FOR JUNIOR HIGH SCHOOL IX

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