Download 973-The Motor Effect - Lesson Plan Including Practical

Triple Science case study
Physics
Name of centre
Ravens Wood School
Name of teacher
Jacqui Hopkinson
Subject
Physics
Specification
AQA
Brief description of case study
Students will investigate the force on a current-carrying conductor in a magnetic field.
We will discuss applications of this, including the motor and the loudspeaker.
Disclaimer
It is important that the content of this case study is your own work and cannot be
attributed to any other source (eg a published scheme of work). Please confirm that this
is your own work by signing below.
Signed: Jacqui Hopkinson
Date: 25 October 2008
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Topic
Range and content
A current-carrying wire in a magnetic field experiences a force at right angles to the
current and the field: describe what the size of this force depends on
How Science Works
1.1 Data, evidence, theories and explanations
Pupils should be taught:
b how interpretation of data, using creative thought, provides evidence to test ideas and
develop theories
1.3 Communication skills
Pupils should be taught to:
a recall, analyse, interpret, apply and question scientific information or ideas
b use both qualitative and quantitative approaches
Extract from Key stage 4 programme of study: http://curriculum.qca.org.uk/key-stages-3-and4/subjects/science/keystage4/index.aspx
Context of the lesson within scheme of learning
This is the first lesson within the GCSE that looks at the relationship between electricity
and magnetism. In Key stage 3 students should have built an electromagnet and know
that its strength can be increased by increasing the current, increasing the number of
turns, and by adding an iron core.
In subsequent lessons they will discover that electricity can be generated by moving a
conductor in a magnetic field. They will use the idea of field lines to explain why a
current is produced only if the wire is not parallel to the field.
Learning objectives
• Observe the motor effect with a single wire in a magnetic field.
•
Investigate qualitatively the effect of the size of the current, the strength of the
magnet and the direction of the current on the size and direction of the force.
•
See the internal workings of an electric motor and a loudspeaker as practical
applications of this.
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Learning outcomes
Students will be able to:
• increase the force on a current-carrying wire in a magnetic field
• explain how this is used in the motor and the loudspeaker
• predict the direction of the force on a current-carrying wire in a magnetic field.
Key concepts/knowledge/skills/understanding addressed by this lesson
The idea that electricity and magnetism are related and they can interact to produce a
force.
Curriculum opportunities
a Research, experiment, discuss and develop arguments.
b Pursue an independent enquiry into an aspect of science of personal interest.
c Use real-life examples as a basis for finding out about science.
d Study science in local, national and global contexts, and appreciate the
connections between these.
e Experience science outside the school environment, including in the workplace,
where possible.
f Use creativity and innovation in science, and appreciate their importance in
enterprise.
g Recognise the importance of sustainability in scientific and technological
developments.
X
h Explore contemporary and historical scientific developments and how they
have been communicated.
Other curriculum opportunity from specification (give details):
Extract from Key stage 3 programme of study: http://curriculum.qca.org.uk/key-stages-3-and4/subjects/science/keystage3/index.aspx?return=/key-stages-3-and-4/subjects/science/index.aspx
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How Science Works progression in this lesson
The aspects of How Science Works being developed are:
In this lesson we will look qualitatively at the effect of current and magnetic field on the
force. Students will see that this could lead to quantitative work if required. They will
come to understand the changing rate of communication and its importance in the
sharing of scientific knowledge and some of the limitations to this.
How are students making progress?
Students will be introduced to the work of Oersted and see how serendipity played a part
in his discovery of electromagnetism. They will discuss briefly how other scientists got to
hear of Oersted’s work and how they would hear about current research. Students will
be asked to suggest possible advantages and disadvantages of the internet in the
sharing of scientific research.
Assessment opportunities in this lesson
When you have explained Fleming’s left hand rule (LHR), set up an example and ask
the students to predict the direction of the movement. It will be possible to see
everybody’s hands and assess who is confused. Students can do the strangest things
and will happily do Fleming’s LHR with their right hand (particularly left-handed students
who have their pen in their left hand).
While discussing Oersted’s experimental work, you can assess who is able to put
forward an argument and who is able to draw on relevant information to support their
opinion.
How ICT is used to support learning
There are some excellent explanations of the motor effect on the web and one of these
can be shown if needed. Alternatively, students can refer to them later to consolidate
their understanding.
One that I sometimes use is:
www.antonineeducation.co.uk/Electronics_AS/Electronics_Module_1/topic_7/electric_motor_effect.htm
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Overview of lesson
Lesson title: The motor effect
Approximate length of lesson: 60 minutes
Starter
Begin by demonstrating Oersted’s experiment. Ask students to explain what
this shows
Main
1 Read an account of Oersted’s experiment and compare the methods of
communicating scientific findings then and now
Plenary
2 Demonstrate the motor effect. Students carry out an experiment to
discover the factors that might affect the size and direction of the force.
Feed back and summarise, and show Fleming’s LHR as a method of
predicting the direction
Introduce and discuss applications of the motor effect. Assess the students’
understanding from their ability to describe the main features of these
applications in terms of the effects they have observed
Homework Students research, summarise and compare the different ways in which
science is shared today and how it was shared in the past and comment on
the benefits and drawbacks of the different methods and approaches
Lesson in detail
Lesson title
The motor effect
Lesson structure
Learning
episode and
timing
Detail
Starter
(10 minutes)
Place a transparent cased plotting compass on an OHP and place a
wire, connected to a 1–2 volt high current (10A) power supply, along
the needle (over and parallel to it), turn the power on and show that
the needle moves. Ask students to suggest reasons for this.
Also show an electromagnet to reinforce the idea of a connection
between electricity and magnetism.
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Main 1
(15 minutes)
Read an account of Oersted’s experiment
(www.practicalphysics.org/go/Resources_13.html)
‘The effect observed by Oersted and his audience was small; noone was very impressed.’ But without it we would not have any
electric motors, loudspeakers and so much more.
Explain how scientists shared information then and ask students to
discuss how things are done now and the advantages and
disadvantages of this.
Main 2
(20 minutes)
Demonstrate the motor effect
Issue students with motor kit magnets (ensure that they have a
North and South facing), a low voltage high current power supply, a
battery, a piece of light insulated wire (as used in the motor kits) and
a variable resistor. This should be in a tray ready for them to use.
Students will see how they can alter the force on the wire. (This will
be qualitative.) You can ask:
• Is the force greater now or before?
•
Did it move faster?
•
How could you change the direction of the force?
Ask several groups to feed back on what they found. Then
summarise this and explain Fleming’s LHR.
To show Fleming’s LHR, demonstrate the motor effect on a big
scale by getting a metal bar to roll across two other metal bars that
are forming part of the circuit. This produces lots of sparks and the
students love it! Using pieces of card to show the direction of the
field and the current make it clearer. Check that all students are
using their left hands as you ask them to predict the direction in
which the bar will roll.
Plenary
(10 minutes)
Show a working loudspeaker (not in a case) and ask students how
this works. How is the sound made louder?
Show a simple d.c. motor kit made up. Ask students to predict which
way it will turn and why.
Homework
(5 minutes)
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By giving at least three examples, discuss how the methods
scientists have used to communicate their findings have changed
over time and discuss advantages and disadvantages of this.
Reflection and evaluation
Although I completed the work in the lesson, it was a bit rushed. I therefore decided to
ask the students to make up the motor kits themselves in the next lesson to allow me
more time to check their understanding and for them to experiment more with the forces
produced and to enjoy seeing how a motor can be made from very simple apparatus.
Starter
I found this essential to remind students of what they had learnt in Key stage 3 and allow
them to remember the work they had done on electromagnets. It was very quick but
allowed students to access a whole collection of relevant knowledge.
Main
Main1: Read an account of Oersted’s experiment
This was included to allow students to understand how science works and in particular
how scientists have communicated their findings over the years. Some also saw how
chance has played a role in scientific developments. Most students saw only the
advantages of modern communication but after discussion some started to point out that
ideas could be stolen or fall into the wrong hands. Some students were able to develop
this further in the homework by discussing examples; others were able to restate it in
their own words.
Main 2: Demonstrate the motor effect
Students were better able to understand the term ‘mutually at right angles’ after
performing the experimental work. Some students were unhappy about the qualitative
nature of the work and discussed methods of measuring the force, but time constraints
did not allow further development of this. All the students enjoyed seeing the wire move
and trying to get it to move faster, or in a different direction. The work was easy and they
finished quickly.
The large-scale demonstration was well received by the students and the cardboard
arrows showing the direction of the current and the field ensured that all students were
able to use Fleming’s LHR correctly to predict the direction in which the bar would roll.
Plenary
This was used for assessment. Most students understood that the cone moved up and
down due to an alternating current in the wire. Many of them were able to think of this
themselves; all were confident to talk about this after an explanation. Many students said
you could increase the volume by increasing the current in the wire, or by altering the
magnetic field (though they could not explain how the latter would be achieved). When
shown the motor, many students correctly predicted the direction of rotation of the coil.
About half the class needed help to understand that the current was travelling in different
directions in each half of the coil, which was a misunderstanding that I had not
anticipated and it was good to get this cleared up.
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Opportunities to differentiate learning
The teacher can vary the questions asked as they walk around the room.
Basic question: What would happen if I reversed the current very quickly?
Advanced question: What would happen if I reversed the magnetic field quickly and how
could I do this? (I have to say that none of my students thought of replacing the
permanent magnet with an electromagnet without a good push from me.)
Basic question: Look round the room. Can you tell me three things that are mutually at
right angles? (Use this if students are having difficulty with this concept.)
Risk assessment
Main hazards identified
Who would
be affected?
Control measures to reduce risk
High current causing
heating of the wires and
possible burns
All students
and staff
Make sure all students are warned of
the risk. Turn off all current between
experiments
Put hand under cold water
immediately if burnt
Opportunities to take this further
As mentioned above, I asked my students to make up the motor kits for themselves in
the next lesson. During that lesson, we discussed the split ring commutator, which we
had not had time to do in this lesson.
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Resources
You can get computer-generated representations of Oersted’s experiment but I personally
think it is far better to show the real thing and using the OHP to project the experiment on
to the whiteboard gives you the best of both.
For the Starter you will need:
•
a transparent cased plotting compass
•
wire
•
a 1–2 volt high current (10A) power supply
•
an electromagnet
Due to the time constraints in this lesson, it is vital that all the demonstrations are set up
and ready to go and that the apparatus for the students is ready in trays for them. For each
tray you will need:
•
motor kit magnets (ensure they have a North and South facing)
•
a low voltage high current power supply
•
a battery
•
a piece of light insulated wire (as used in the motor kits)
• a variable resistor
Metal bars and pieces of card to demonstrate Fleming’s LHR
A working loudspeaker (not in a case)
A simple d.c. motor kit made up
If you intend to use the internet for any visual aids, get them ready and saved to your
computer. Ones I have used include:
http://www.antonineeducation.co.uk/Electronics_AS/Electronics_Module_1/topic_7/electric_motor_effect.htm
www.practicalphysics.org/go/Resources_13.html
Bibliography
National Strategies Framework for Teaching Secondary Science: Overview and Learning
Objectives (2008) www.standards.dcsf.gov.uk/secondary/frameworks
Science Programme of Study for KS3 (Extract from National Curriculum) (QCA 2008)
http://curriculum.qca.org.uk/key-stages-3-and4/subjects/science/keystage3/index.aspx?return=/key-stages-3-and4/subjects/science/index.aspx
Science Programme of Study for KS4 (QCA 2008) http://curriculum.qca.org.uk/keystages-3-and-4/subjects/science/keystage4/index.aspx
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