Form 5 Chapter 3

What is an electromagnet? electromagnet? •

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

Trusted by over 1 million members

Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial Cancel Anytime.













Magnetic field













•

Determine Determine the direction of magnetic field current-- carrying car arry ryin ing g wire wire wir e around a current













Plan View of the Magnetic Field













1. Straight wire, •

•

A magnetic field will be generated generated when a current flows through a wire. The magnetic field forms by straight wire are around the wire.













Strength of the Magnetic Field The strength of the magnetic field form by a current carrying conductor depends on: 1.

the magnitude of the current. stronger current w around the wire.

pro uce a stronger magnet c e

2. the distance from the wire. wire. The strength of the field















2. Coil •

Grip the wire at one side of the coil with your right hand, with thumb pointing along the direction of the current.













Factors affecting the strength There are 2 ways to increase the strength of the magnetic field:













3. Solenoid •

A solenoid is a long coil made up of a numbers of turns of wire.













Strength of the Magnetic Field The strength of the magnetic field can be increased by













Application of Electromagnet















Electric Bell













Magnetic Relay













Circuit Breaker













Telephon elephone e Earpiece Earpiece



















































































































































Electromagnetic Induction













Electromagnetic Induction •

•

•

When a magnet is moved into and out of the solenoid, magnetic flux is being cut by the coil. The cutting of magnetic flux y e w re co n uces an e.m. e. m.ff in the the wi wirre. When the solenoid is connected to a closed circuit,













Faraday's Law •

Faraday's Law states that the magnitude of the induced e.m.f is directly proportional to the rate of change of magnetic flux through a flux being cut.













Lenz's Law •

Lenz's Law states that the induced current always flows in the direction that opposes the change in magnetic flux.













Fleming's Right Hand Rule (Generator Rule)

•

Fleming's Right-Hand Rule is used to determine the direction of the induced current that flows from the wire when there is field















Direct Current Current Generator Generator •

A simple simple d.c genera generato torr essenti essentially ally the converse of a d.c. motor with its battery













DC Generator Generator - Display of the Voltage Voltage in a CRO CRO •

•

Initially the armature is vertical. No cutting of magnetic flux occurs and hence induced current does not exist. After rotating rotating by 90°, the t he armature is in the horizontal position. The change in magnetic flux is maximum and hence the













A.C generator •

Generator Generator can be modified modified to an a.c generator generator by replacing its commutat commutators ors with two (separate) (separate) slip rings.













AC Gener Generator ator - Display of the Voltage Voltage in a CRO •

•

•

The armature is initially at the vertical position. No magnetic flux is cut and hence no induced current exists. When the armature rotates, the change in magnetic flux increases and the induced current increases until its maximum value at the horizontal position. As the armature continues on its rotation, the change in













Differences between DC and AC generator



























Direct Current













Alternating Current













Root Mean Square Voltage













Direct Current and Alternating Current with Capacitor

Form 5 Chapter 3

Recommend Documents