Download Student practical Name Class Date Charging by friction

P4.1
Student practical
Name ......................................................................
Class ..................
Date ......................
Charging by friction
Specification references:
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P.2.5.1 Static charge
P.2.5.2 Electric fields
MS 5b
WS 1.2, 3.6
Aims
In this activity you will explore the causes and effects of static electricity. You
will practise explaining static electric effects and describing electric fields, by
answering a series of questions about the experiment and demonstration and
then creating a revision guide about electrostatics.
Learning outcomes
After completing this practical you should be able to:
 describe how to charge objects and how charged objects affect each other
 describe, in terms of electrons, how objects become charged
 use the idea of electric fields to explain why charged objects interact, and
describe the shape of the field and lines of force around a charged sphere
 explain why sparks can be produced by charged materials.
Safety
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The Van de Graaff demonstration should not be done if anyone in the room
has a heart condition or has a pacemaker fitted.
Electronic devices such as computers and mobile phones should be kept
away from the Van de Graaff generator.
Equipment
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Clamp stand with boss and clamp
Card
Cotton or nylon thread
2 Perspex rods
2 polythene rods
Cloth
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
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P4.1
Student practical
Name ......................................................................
Class ..................
Date ......................
Setting the scene
Most objects, most of the time, are neutral – they have zero charge overall.
Electrostatics is the study of static electricity. Static electricity is when an object
(or part of an object) is not neutral, but is positively or negatively charged. We
notice static electricity when we see ordinary objects attracting or repelling each
other, or when we ourselves become charged and then get an electric shock
when charges flow through us as we touch something. Charged objects exert
forces on each other because they are affected by each other’s electric fields.
Method
Experiment: charged rods
1 Create a hammock which can hold a rod horizontally and which can be hung
from the clamp so that the rod swings freely.
2 Rub two insulating rods of the same type with the same type of cloth.
3 Rest one of the rods in the hammock so that it hangs horizontally and can
swing freely.
4 Hold the other rod and bring one end of it close to one end of the hanging rod.
5 Repeat steps 1–4 using insulating rods of two different types.
Demonstration: van de Graaff generator
Your teacher will demonstrate charging and discharging a Van de Graaff generator.
Results
Write down your observations from your experiment in a clear and organised way
(so that someone else could read them and find out what you observed).
Your teacher may ask you to record your observations from the demonstration
as well.
Questions
1
If two rods of the same material are rubbed with the same type of cloth, they
gain the same type of charge. What did your experiment show you about
objects with the same type of charge?
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
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P4.1
Student practical
Name ......................................................................
Class ..................
Date ......................
(1 mark)
2
In your experiment you will have also seen that the two rods of different material
attracted each other. What does that tell you about the charges on the two rods?
(1 mark)
3
Circle the correct words to complete the following sentences.
a The nucleus of an atom contains protons and electrons/neutrons.
b When an object gains/loses protons/electrons, it becomes negatively charged.
c When an object gains/loses protons/electrons, it becomes positively charged.
d A charged atom is called a/an nucleus/ion/electron.
(1 mark)
(1 mark)
(1 mark)
(1 mark)
Extension
4
A charged object creates an electric field around itself. The electric field has
an effect on any other charged objects which are in it. A field can be sketched
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
3
P4.1
Student practical
Name ......................................................................
Class ..................
Date ......................
by drawing lines of force which show the path a small positive charge would
follow because of the field.
a Sketch the electric field around a positively charged sphere (like the top of
the Van de Graaff generator)
(3 marks)
b
How would the field lines change if the sphere were negatively charged
instead?
(1 mark)
c
The effect of the electric field is weaker at larger distances from the
sphere. How do the field lines show this?
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
4
P4.1
Student practical
Name ......................................................................
Class ..................
Date ......................
(1 mark)
5
We usually think of air as an insulator, and it is true that air does not usually
conduct electricity.
a What did you observe that showed that a current was passing through air?
(1 mark)
b
Give one condition needed to make a current pass through air.
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
5
P4.1
Student practical
Name ......................................................................
Class ..................
Date ......................
(1 mark)
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
6
P4.1
Student practical
Name ......................................................................
Class ..................
Date ......................
Student follow up
Write a mini revision guide about electric fields and static electricity. It should include:
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a labelled diagram showing the particles inside an atom
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what you need to do to charge an object
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an explanation of how objects become positively or negatively charged
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a description of the forces between charged objects
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an explanation of why charged objects interact, in terms of electric fields
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(extension) a sketch of an electric field around a small negatively charged
sphere, with a description of the way the field’s effect changes, depending
on the amount of charge on the sphere and the distance from the sphere
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(extension) an explanation of how a spark can travel between two objects.
Your writing should have a clear structure and use scientific language.
Present the information in a way that makes it as memorable as possible (so not
just as a single block of text).
© Oxford University Press 2016
www.oxfordsecondary.co.uk/acknowledgements
This resource sheet may have been changed from the original.
(2 marks)
(1 mark)
(3 marks)
(3 marks)
(2 marks)
(5 marks)
(3 marks)
(2 marks)
(1 mark)
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