Download Electric Circuits Tutor Notes

60 minute physics
Nine hands-on activities:
with GCSE Physics curriculum links
Electric
circuits
Mapping data
Digital
Electric
circuits
Machines &
electromagnets
Flight &
movement
Light
Storing energy
Forces &
motion
Changing
states
Electric circuits
STEM engagement materials developed for the Royal Air Force
Electric circuits
This activity forms part of a suite of physics-related activities developed by West Yorkshire STEM in
collaboration with the University of Leeds. They have been funded by the Royal Air Force to encourage
pupils to think positively about STEM generally and physics in particular. Each activity has been designed
to be interactive and linked to GCSE physics specifications of OCR and AQA. Stretch or extension activities
are provided in the content for additional follow-up beyond the session.
Electric
circuits
To run this activity you will need:
•A flat teaching space with enough room for small groups
(of around 4 pupils) to work together to work through
activities.
•Powerpoint facilities to introduce the content and activities
(using ‘Electric_circuits.pptx’).
•1 copy of the handout ‘Making speakers.pdf’ per student.
(for building speakers)
•1 Double ended audio jack, cut in half per student.
•1 10mm diameter, 5mm height Neodymium magnet per student.
•1 5cm width, 30 cm length of scrap paper per student.
•1 Plastic or Styrofoam cup per student.
•1 10m of 0.15mm diameter enamel coated copper wire per student.
•1 Multimeter or Ohmeter per class.
•5 Hot glue guns and glue gun sticks per class.
•10 pairs of scissors per class.
•10 Rolls of electrical tape per class.
•20 sheets of very fine sand paper per class.
•1 ‘Certificate of completion’ for each student - produced as
part of these materials (Certificate_electric_circuits.pdf)
Level: KS3/KS4
GCSE science curriculum links: electricity / electromagnetism
Objectives of the session
•Understand electrical potential and how current flows around a circuit
•Understand electromagnetism
•Demonstrate knowledge of how speakers employ electricity to function
Session length: 60 mins
Session overview
•Presentation (20 mins)
•Building speakers (40 mins)
Extension: Teaching Advanced Physics (TAP): electric current
This online resource looks at basic electrical ideas, particularly current, potential difference and
energy. It has been developed and produced by the Institute of Physics and is available at:
http://tap.iop.org/electricity/current/index.html.
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Slide 1
Introduction to the session
•Introduce yourself as the facilitator and outline (briefly)
your STEM background.
•Ask STEM Ambassadors (if present) to (briefly) introduce
themselves and to say which STEM discipline/industry
they are from.
Slide 2
Gravitational fields
•Mass ‘M’ has gravitational field ‘G’
•‘Gravitational’ means that the field is due to gravity
•All ‘masses’ have gravitational fields, people have
gravitational fields, atoms have gravitational fields, but the
‘magnitude’ or ‘how big ‘ the gravitational field is depends on
how big the mass is
•A good example of a large mass is the earth, it has a
gravitational field that pulls the moon towards it
•A gravitational field is illustrated by ‘field lines’, direction
of pull is denoted by arrows
•A gravitational field exists only because mass ‘M’ exists –
this is an important point
•For all field lines, the closer they are together, the greater the force of the field
•d1 shows a smaller distance between the field lines than d2, so the force of the field is larger
closer to mass ‘M’
•This is shown is the second diagram, the force exists all around mass ‘M’, the darker green is a
stronger force field and the lighter green is the weaker force field.
Slide 3
Electric fields
•In an atom, we have three things: protons (positively
charged), neutrons (neutrally charged) and electrons
(negatively charged)
•An electric field only exists around things that are
‘charged’
•So in an atom, the things that have a ‘charge’ are protons
and electrons
•The electric field only exists because there is a charge
present (whether it’s positive or negative)
•Protons have a repelling electric field while electrons have
an attractive electric field, just like the gravitational field.
3
Slide 4
Magnetic fields
•Here we have a diagram of a wire that is full atoms that have
both positive and negative charges
•Like every charge has an electric field, every moving charge
has a magnetic field
•Magnetic fields only exist because there is a moving charge,
specifically, electrons moving through the wire
•The magnetic field produced ‘wraps’ around the wire, and
we’ll learn how this happens in the next few slides.
Slide 5
Permanent magnets
•All permanent magnets have a north and south pole, and
the magnetic fields are illustrated, one again, using field
lines
•The magnetic field goes from the north to the south pole
Slide 6
Permanent magnets (continued)
•We can visualize the magnetic field when we place iron
filings around a magnetic, we can see the fields going from
the north to the south pole.
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Slide 7
Magnetic field in an electric coil
•If we create a coil out of many wire loops stacked on top of
each other, and send current through the coil, you get a lot
of magnetic field around the wire
•The magnetic field of all the loops add up together, and
you get a magnetic field that looks very much like a field
around a bar magnet
•We get a north pole and a south pole around the coil,
creating an electromagnet: a magnet created using an
electric current
•The more loops we have the stronger the magnetic field.
Slide 8
How speakers work
•The job of a speaker is to convert electrical signal from
the sound source into an audible sound: we start out with
a permanent magnet with a north and south pole.
Slide 9 and 10
How speakers work (continued)
•We then create an electromagnetic coil around the
permanent magnet, which has its own magnetic field
around it with a north and south pole when current flows
through the wire. The permanent magnet is fixed, but the
electromagnet can move.
•This coil behaves like a normal permanent magnet but with
one handy property: when the flow of current reverses
direction, the poles on the magnet flip – where the north
pole becomes south and vice versa.
•As pulses of electricity pass through the coil, the direction
of the magnetic fields rapidly change and the poles of the
electromagnet switch. This means that electromagnet is
attracted and repelled from the permanent magnet and
vibrates back and forth.
•The electromagnet is attached to a diaphragm or cone that
amplifies these vibrations, pumping sound waves into the
surrounding air and towards your ears.
5
Slide 11
Let’s make a speaker
•Provide pupils with a copy of the handout:
‘Making speakers.pdf’
Slide 12
Steps to assemble speaker 1
•(1) Stick magnet to the inside-bottom of the cup.
•(2) Wrap copper wire coil and stick to outside-bottom of
cup.
•(3) Join copper wire to audio jack.
Slide 13
Steps to assemble speaker 2
•(1) Stick magnet to the bottom of the cup.
•(2) Wrap copper wire coil and stick to outside-bottom of
cup.
•(3) Join copper wire to audio jack.
6
Slide 14
Steps to assemble speaker 3
•Stick magnet to the bottom of the cup.
•Wrap copper wire coil around paper tube & hot glue
around magnet.
•Join copper wire to audio jack.
Slide 15
Steps to assemble speaker 5
•(1) Stick magnet to the inside-bottom of the cup.
•(2) Wrap copper wire coil and stick to outside-bottom of
cup.
•(3) Sand ends of copper wire & join to audio jack.
•(4) Now test your speaker!
Slide 16
RAF examples: electromagnets
•Using electromagnets isn’t something new. The RAF were
using them a long time ago.
•Look at this example of a magnet fitted to an aircraft.
•It was used the detect mines during the Second World
War.
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