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1. MOTORS

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2. GENERATORS

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Click to watch the video:

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Discovered by Hans Christiaan Oersted

This effect is called the electromagnetic effect

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MAGNETIC FIELD = The region around a magnet where another magnetic material will experience a force.

Magnetic field direction is N to S outside the magnet.

Magnetic field direction is S to N inside the magnet.

Magnetic field lines representing the strength and direction of the magnetic field.

Magnetic field lines are continuous lines, forming closed loops.

ONLY THREE METALS ON EARTH ARE NATURALLY MAGNETIC:

Fe, Co, Ni. (they are called ferromagnetic)

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MAGNETIC FIELDS CAN BE PRODUCED BY ELECTRIC CURRENTS

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MAGNETIC FIELDS CAN BE PRODUCED BY ELECTRIC CURRENTS

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Magnetic fields are produced by electric currents, which can be currents in wires (or microscopic currents associated with electrons in atomic orbits).

EFFECTS OF AN ELECTRIC CURRENT (I.E. MOVING CHARGE):

Heating

Magnetism

In electrodynamics we study the magnetic effect resulting from current flowing in a wire.

When charge moves in a medium, it generates a magnetic field perpendicularly around that medium.

This is electromagnetism (Below is an electromagnet).

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The right hand rule is used to find the direction of the magnetic field lines around a current carrying conductor (CCC).

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Curly fingers = points in direction of current in solenoid.
Thumb = points to NORTH POLE generated by current in the solenoid.

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GCSE Science (1-9): Physics: Fleming's left hand rule and the motor effect

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Force on a Current Carrying Wire in a Magnetic field

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CURRENT-CARRYING CONDUCTOR PLACED IN 2ND MAGNET FIELD

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CURRENT-CARRYING CONDUCTOR PLACED IN 2ND MAGNET FIELD

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Both magnetic fields interact.

The magnetic field between the opposite poles and the magnetic field around the current-carrying conductor reinforce each other on one side of conductor

and cancel each other on the other side.

A Lorentz force is created = the force acting on the ccc in a MF

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HAND RULES EXPLAINING INTERACTION BETWEEN CURRENTS AND MAGNETIC FIELDS

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HAND RULES EXPLAINING INTERACTION BETWEEN CURRENTS AND MAGNETIC FIELDS

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Right Hand Grip Rule

Fleming Left Hand Rule

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See-Thru Science: Right and Left Hand Rules

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Electricity + magnetism = motion, thanks to the Lorenz force. Find out how. https://nationalmaglab.org/education/magnet-academy

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The Motor Effect | GCSE Physics | Doodle Science

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Flux = the amount of “something” (electric field, magnetic field) passing through a surface.

Total magnetic flux depends on:

Strength of the field

Size of the surface it passes through

Orientation of the surface

For a loop of area (A) in the presence of a uniform magnetic flux density (B), the magnetic flux (Ф) passing through the loop is:

Ф = BA cos θ

where θ = angle between magnetic flux density (B) and the normal to the loop of area (A).

where B = the magnetic field strength (in Tesla)

where A = area of the coil loop

Unit for Ф = Wb (Weber)

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THE COMPONENT OF THE MAGNETIC FIELD VECTOR PARALLEL TO THE NORMAL IS WHAT IS USED IN CALCULATIONS (Bcosθ)

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THE COMPONENT OF THE MAGNETIC FIELD VECTOR PARALLEL TO THE NORMAL IS WHAT IS USED IN CALCULATIONS (Bcosθ)

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MAGNETIC FIELD STRENGTH (symbol B, unit Tesla)

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MAGNETIC FIELD STRENGTH (symbol B, unit Tesla)

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DEF = magnetic flux density (B) is a representation of the magnitude and direction of the magnetic field.

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Electromagnets and Electromagnetic Induction | GCSE Physics | Doodle Science

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ALTERNATOR

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DEF:

Faraday's Law = The emf induced in a coil/conductor is directly proportional to the rate of change of magnetic flux linkage.

Flux linkage = The product of the number of turns on the coil and the flux through the coil (NФ)

The electromotive force (Voltage) generated in a generator is given by Faraday's Law, below.

Emf is affected by these factors:

Number of turns in the coil

Rate of change of flux

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DRAW AND INTERPRET GRAPHS OF MAGNETIC FLUX LINKAGE VS. TIME

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DRAW AND INTERPRET GRAPHS OF MAGNETIC FLUX LINKAGE VS. TIME

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For an AC generator, indicating how:

the position of the NORMAL TO THE COIL relative to the magnetic field relates to the flux linkage magnitude.

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Def:
Lenz's Law = The induced current in a coil/conductor flows in a direction so as to set up a magnetic field to oppose the change in the magnetic flux.

The negative sign in Faraday's law is due to the fact that:

The emf induced in the coil acts to oppose any change in the magnetic flux.

Work is done to push the permanent magnet against the coil's induced magnetic field.

Energy is conserved (Emechanical --> Eelectrical).

Lenz's Law:

gives the direction of an induced EMF which induces a current flow.

the current flows in a direction to oppose the change (an increasing or decreasing magnetic field) causing it.

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How AC Generator Produces Electricity? - Physics || Extramarks

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Use this hand rule to determine the direction of flow of CURRENT induced within the coil.

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What is Electromagnetic Induction? | Faraday's Laws and Lenz Law | iKen | iKen Edu | iKen App

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A generator is a device that converts E k --> E electric. It is a motor in reverse.

In a motor:

A current is passed through a coil in a magnetic field, causing a force and the coil MOVES. A motor works on the principle of the motor effect.

In a generator:

A coil is rotated through a magnetic field, CAUSING A CURREN T to flow in the coil as the wire cuts across the magnetic field. This causes a changing magnetic field.

A generator works on the principle of electromagnetic induction.

Induction = the production of current in a conductor as it moves through a changing magnetic field.

Faraday's Law of Induction applies in generators, stating that:

if a wire is moved back and forth in a magnetic field, it cuts across the lines of magnetic flux. This magnetic field pushes on electrons in the metal. This movement of electrons is electrical flow.

The strength of a generator or motor depends on:

"B" - Strength of the magnetic field (flux density of the magnet)

"I"  - Current flowing or generated in the coil

"ℓ" - Length of the conductor in the magnetic field

"θ" - Angle between the conductor and the fixed magnetic field

Use this formula for calculations:

F = B x I x ℓ x sin θ

Also: F = Bqv ; q=charge, v=speed of rotor

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RMS Vs Peak Values Part 1 - What is Root Mean Square?

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AC Generator = An ALTERNATOR
DC Generator = A DYNAMO

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GCSE Science Physics (9-1 Triple) The Alternator and Dynamo

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Factors affecting induced emf:

Position of the coil

If parallel to the external magnetic field (B), then flux lines are not 'cut' and zero induced emf is generated.

If perpendicular to an external magnetic field (B), then flux lines are being 'cut' and an induced emf is generated.

Strength of the magnetic field

Number of turns on the coil

Area of the coil

Coil wound around an iron core or not.

Rotation speed of the coil

i.e. Rate of change in magnetic flux or rate with which coil "cuts" across the permanent magnetic field

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Power plants have generators rotated by water or steam.

Car alternators charge battery when driving.

Diesel/petrol generators as alternative power supply when off-grid.

Moving coil microphones use alternators.

Sound waves vibrate a membrane which move a coil in a magnetic field.

This induces a varying current which gets amplified and fed to a loudspeaker.

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LENZ'S LAW

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PURPOSE OF A TRANSFORMER = It is used to increase or decrease AC voltage.

The Number of turns on the primary and secondary coils affect the input and output voltages.

What type of transformer is this?

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Electromagnetic Induction Explained: Self Induction, Lenz's law,  and Transformers

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Transformers Physics Problems - Voltage, Current & Power Calculations - Electromagnetic Induction

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Alternating current electrically alternates in polarity from a positive to a negative (and vice versa).

Our household power is generated as AC in power stations.

Most devices is not compatible with AC, but uses DC to operate.

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Changing AC to DC - by aid of a bridge rectifier.

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CAPACITOR SMOOTHENS THE PULSATING DC CURVE

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CAPACITOR SMOOTHENS THE PULSATING DC CURVE

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An electronic component that allows electricity flow in one direction only.

Like a sort of water VALVE.

Signal diodes

Rectifier diodes

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In 1909 he jointly received the Nobel Prize for his groundbreaking contributions to wireless radio and television.

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The Diode & it’s function in rectification

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The Diode & it’s function in rectification

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BRIDGE (DIODE) RECTIFIER IN A REAL CIRCUIT

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BRIDGE (DIODE) RECTIFIER IN A REAL CIRCUIT

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EXERCISE 10

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ELECTROSTATIC VS GRAVITATIONAL FIELDS IN ACTION - BUILD YOUR OWN PARTICLE ACCELERATOR!  

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ELECTROSTATIC VS GRAVITATIONAL FIELDS IN ACTION - BUILD YOUR OWN PARTICLE ACCELERATOR!  