*Chapter 33.1Magnetic Effect of a Current-carrying conductor

*ElectromagnetsMagnet:Show magnetism (attract metal) over a long periodElectromagnet:Temporary magnetOnly show magnetism while current flowing

An electromagnet can be made by sending an electric current through a coil of wire wound around an iron core.

*Switch onCurrent flows Magnetic field is produced ( which is produced by current )Wire / coil is magnetisedAttracts pins (metal)+_pinsSwitch oncoilMagnetic field

*Switch off+_pinscoilMagnetic field

Magnetic Field Patterncan be represented by field lines that show the shape of the field. magnetic field lines which are close together represent a strong field. the field direction is defined as the direction indicated by a compass needle placed in the magnetic field.

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*Direction can be determined usingRight-hand grip ruleor called Amperes right-hand grip ruleThumb:direction of current 4 fingers:direction of magnetic field

Thumb: magnetic field4 fingers: current

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*Pattern & Direction of Magnetic FieldBar magnetElectromagnet Straight wire Circular coil Solenoid

*Pattern & Direction of Magnetic Field a) bar magnetS

*Pattern & Direction of Magnetic Field of electromagnetExperiment :To study the pattern and direction of the magnetic field in aStraight wireCircular coilSolenoid Pattern: see pattern of iron (line? Circular?)Direction: direction of compass

*b) Straight wirePattern:CircularCloser if near to the wire ( stronger strength of magnetic field )

Direction: Clockwise

*Straight wire + _ _+Pattern:CircularCloser if near to the wire ( stronger strength of magnetic field )

Direction: Anti-Clockwise

*c) Circular coil_+

*Circular coil_+

*d) Solenoid+_

*+_Solenoid

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*Comparepattern & direction of magnetic field of a bar magnet with a solenoid They are the same !Bar magnetSolenoid

*Factors that affect the strength of the magnetic field of an electromagnetTurns of coilCurrent Type of iron core

*The strength of the magnetic field of an electromagnet increases whenThe number of turns of coil increasesThe current flows increasesThe soft iron core is used

Application of Electromagnet Electric Bell*

When the bell push is pressed, a current flows in the coils of the electromagnet, causing it to be magnetized. The magnetized electromagnet attracts the soft-iron armature, causing the hammer to strike the gong. The movement of the armature breaks the contact and causes the electromagnet to lose it magnetism. The light spring pulls the armature back, remaking the contact and completing the circuit again. The cycle is repeated so long as the bell push is pressed and continuous ringing occurs.

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Magnetic RelayCircuit BreakerTelephone Ear-piece*

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