2 Electromagnetism

8/12/2019 2 Electromagnetism

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Electromagnetism

Syllabus

Lesson 01 The Motor Effect

Lesson 02 Induction


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Syllabus - Single Science IGCSEMagnetism

6.2 recall that magnets repel and attract other magnets, and attract magnetic substances

6.3 recall the properties of magnetically hard and soft materials

6.4 understand the term magnetic field line

6.5 understand that magnetism is induced in some materials when they are placed in a magnetic field

6.6 sketch and recognise the magnetic field pattern for a permanent bar magnet and that between two bar magnets 6.7 know how to use two permanent magnets to produce a uniform magnetic field pattern

Electromagnetism

6.8 recall that an electric current in a conductor produces a magnetic field round it

6.9 describe the construction of electromagnets

6.10 sketch and recognise magnetic field patterns for a straight wire, a flat circular coil and a solenoid when each is carrying a current

6.11 appreciate that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field

6.12 recall that a force is exerted on a current-carrying wire in a magnetic field, and, how this effect is applied in simple d.c. electric motors

and loudspeakers 6.13 predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field

6.14 recall that the force on a current-carrying conductor in a magnetic field increases with the strength of the field and with thecurrent

Electromagnetic induction

6.15 recall that a voltage is induced in a conductor when it moves through a magnetic field or when a magnetic field changes through a coil; alsorecall the factors which affect the size of the induced voltage

6.16 describe the generation of electricity by the rotation of a magnet within a coil of wire and of a coil of wire within a magnetic field; also

describe the factors which affect the size of the induced voltage 6.17 recall the structure of a transformer, and understand that a transformer changes the size of an alternating voltage by having different

numbers of turns on the input and output sides

6.18 explain the use of step-up and step-down transformers in the large-scale generation and transmission of electrical energy

6.19 recall and use the relationship between input (primary) and output (secondary) voltages and the turns ratio for a transformer

secondary turns / primary turns = output (secondary) voltage / input (primary) voltage

6.20 recall and use the relationship

input power = output power VP IP = VS IS for 100% efficiency


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Syllabus Double IGCSEMagnetism and electromagnetism

understand the term magnetic field line (P2.19)

recall that an electric current in a conductor produces a magnetic fieldround it (P2.20)

recall that a force is exerted on a current-carrying wire in a magnetic field,and, how this effect is applied in simple d.c. electric motors andloudspeakers (P2.21)

predict the direction of the resulting force when a wire carries a

current perpendicular to a magnetic field (P2.22) recall that the force on a current-carrying conductor in a magnetic field

increases with the strength of the field and with the current (P2.23).

Electromagnetic induction

recall that a voltage is induced in a conductor when it moves through a

magnetic field or when a magnetic field changes through a coil; also recallthe factors which affect the size of the induced voltage (P2.24)

describe the generation of electricity by the rotation of a magnet within acoil of wire and of a coil of wire within a magnetic field; also describe thefactors which affect the size of the induced voltage (P2.25).


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The Motor Effect 08/06/2014

Aim: To use Flemmings Left Hand Rule To explain how a motor works To construct a motor


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Fields Bar Magnets Single Science Only

handout
http://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Handout%20Magnetic%20Fields.dochttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Handout%20Magnetic%20Fields.doc


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Opposite PolesSingle Science Only


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Same PolesSingle Science Only


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Fields due to Current


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Single Science Only

Single Coil of Wire Solenoid


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Magnetic Field Lines There are magnetic field lines around every

Magnet

Electrical wire (with current flowing through it)

Anything magnetic in the field will experience a force

Movie
http://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Movie%20Magnetism%20Fields%20Clip%20-%20SIA.mpghttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Movie%20Magnetism%20Fields%20Clip%20-%20SIA.mpg


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Wire in a magnetic field


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The Catapult (Motor) Effect


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Motor Effect If a conductor carrying an electric current moves

through magnetic field lines at right angles it will

experience a force. A charged particle will experience the same effect


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Fleming's left hand rule


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Demo with Motor Effect Apparatus


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Increasing the Size of the Force


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The motor effect: true or false?

Si l S i O l


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Exam Question

Single Science Only

Si l S i O l
http://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Exam%20Question%20-%20Field%20Lines%20-%202005%202H%204.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Exam%20Question%20-%20Field%20Lines%20-%202005%202H%204.pdf


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Exam Question

Single Science Only
http://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Exam%20Question%20-%20Field%20Lines%20-%202005%202H%204.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Exam%20Question%20-%20Field%20Lines%20-%202005%202H%204.pdf


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Coil in a Magnetic Field


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How does an electric motor work?


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Demo Motor

l l


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DC electric motor simulation

H d h?


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Would the same strength motor be used in both of these?

How can the strength of an electric motor be increased?

How do we increase motor strength?

increase the strength of the magnet

increase the current flowing through the coil

increase the number of turns on the coil

Worksheet
http://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Worksheet%20motors.dochttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Worksheet%20motors.doc


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The Motor Effect recap

Aim: To use Flemmings Left Hand Rule To explain how a motor works To construct a motor


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Induction 08/06/2014Aim:To observe and define induction

To explain how electricity is generated


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Exam Question
http://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Exam%20Question%20-%20Motor%20Effect%20-%202005%202H%2015.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2001%20-%20Exam%20Question%20-%20Motor%20Effect%20-%202005%202H%2015.pdf


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I d i t i i


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Inducing current in a wire

Wh t i l t ti i d ti ?


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What is electromagnetic induction?

Current Carrying Wire + Magnetic field = MotionMotion + Magnetic field = Current in Wire

Changing Magnetic field = Current in wire

If they are at right angles to each other

I d i t i il


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Inducing current in a coil

I d ti


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Induction

If a magnet is moved near a coil of wire a current is inducedin the wire

Faster motion, bigger current

Stronger magnet, bigger current

More turns, bigger current

Change direction of motion, change direction of current

F t ff ti i d d t


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Factors affecting induced current

H n m ti n p d nt?


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How can motion produce a current?

What are Generators?


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A generatoris a device that converts mechanical energy into electricalenergy. It is the opposite of an electric motor.

Power stations use generators to produceelectricity on a large scale.Mechanical energy is provided by rotatingturbines that can be powered by:

What are Generators?

high-pressure steam in coal, oil, gas and nuclear power stations

wind in wind turbines

falling water in hydroelectric power stations

How do AC generators work?


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How do AC generators work?

AC generator simulation


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AC generator simulation

Induction: true or false?


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Induction: true or false?

What is a transformer?


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The voltage of an alternating current can be changed using a devicecalled a transformer.

The alternating current inthe primary (input) coilproduces an alternatingmagnetic field.

What is a transformer?

A transformer contains twocoils that are wound around asoft iron core.

iron core

primarycoil

secondarycoil

This alternating magnetic fieldinduces an alternating currentin the secondary (output) coil.

How does a transformer change voltage?


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The voltage inducedin the secondary (output) coil depends on thenumber of turnson the primary and secondary coils.

How does a transformer change voltage?

A step-up transformerhasmore turns on the secondarycoil and so increases voltage.

A step-down transformerhasfewer turns on the secondarycoil and so decreases voltage.


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How are transformers used to supply electricity?

Transformers


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Transformers Transformers are used to change the voltage from the Primary

(input) to the Secondary (output)

They only work with a.c. (alternating current)

Input (Primary) Voltage = Number of Primary Turns

Output (secondary) Voltage Number of Secondary Turns

Example Question: Input voltage = 230 V

Primary turns = 10000

Secondary turns = 500

What is the secondary voltage?

Worksheet
http://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2002%20-%20Worksheet%20Transformers.dochttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2002%20-%20Worksheet%20Transformers.dochttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2002%20-%20Worksheet%20Transformers.dochttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2002%20-%20Worksheet%20Transformers.doc


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Exam QuestionSeparate Science only

Exam Question
http://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2002%20-%20Exam%20Question%20-%20Transformers%20-%202006%202H%2015.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2002%20-%20Exam%20Question%20-%20Transformers%20-%202006%202H%207.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2002%20-%20Exam%20Question%20-%20Transformers%20-%202006%202H%207.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_1/Electricity%20-%20Electromagntism%20-%2002%20-%20Exam%20Question%20-%20Transformers%20-%202006%202H%2015.pdf


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Induction 08/06/2014

Aim:To observe and define inductionTo explain how electricity is generated

USE ME IN THIS PRESENTATION


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