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Marr College
Science
Electricity
Learning Outcomes and
Summary Notes
Learning Intentions
By the end of this unit I will be able to
1.
Describe how static charges behave.
2.
State that electrons have a negative charge
3.



4.
Describe what happens when
Two positive charges are close to each other
Two negative charges are close to each other
One positive and one negative charge are close to each other
State that in a circuit only electrons can move.
5.
Describe the movement of electrons around a complete circuit.
6.
State that the movement of electrons is called a current.
7.
8.
Describe how an ammeter is used to measure the current
through a circuit.
State that the unit of current is the ampere or amp (A).
9.
State that a battery, power supply or mains provides a voltage.
10. State that the voltage pushes the electrons round the circuit.
11. Describe how a voltmeter is used to measure the voltage across
components in a circuit.
12. State that the unit of voltage is the volt (V).
13. Draw the symbols for an ammeter and a voltmeter
14. Recognise and build a series circuit.
15. Draw a series circuit with an ammeter to show how the current
is measured.
16. Draw a series circuit with a voltmeter to show how the voltage
is measured.
17. Calculate current and voltage values in a series circuit.
18. Recognise and build a parallel circuit.
19. Draw a parallel circuit with an ammeter to show how the
current is measured.
20. Draw a parallel circuit with a voltmeter to show how the voltage
is measured.
21. Calculate current and voltage values in a parallel circuit.
22. Design circuits, including circuits, to show the advantages of
parallel circuits in everyday situations.
23. Design a fruit battery.
24. Describe how to investigate the factors that affect the voltage
produced by a fruit battery.
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Electric Charge
 There are two types of electric charge called positive (+) and
negative (-).
 Tiny particles that are part of atoms carry electric charge.
 Protons carry positive (+) charge.
 Electrons carry negative (-) charge.
 Electrons have the ability to move. It is the movement of
electrons that allows electrical appliances to operate.
 Most objects are electrically neutral. They have no overall
charge. This is because they have an equal balance of
positive and negative charge.
 If a neutral object gains extra electrons it gets an overall
negative charge.
 If a neutral object loses electrons it gets an overall positive
charge.
 If two objects with the same charge are brought close to each
other, they repel (push away from each other).
 If two objects with opposite charges are brought close to
each other, they attract (move towards each other).
 Like charges repel.
 Opposite charges attract.
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Electric Current
 An electric current is a flow of electrons. Since electrons
have a negative charge, current flow towards objects with a
positive charge. (opposites attract).
 The size of a current is measured in units called
Amperes (A). So, for example, the current in an electric
kettle could be 5 A.
 The device used to measure current is called an ammeter.
Electric Circuits
 A circuit is a path for current to flow round. Current will flow
towards the positive side of the battery.
 All metals are conductors. Conductors are materials that are
good at allowing current to flow.
 Carbon is a conductor, but it is a non-metal.
 All other non-metals are insulators. Insulators do not allow
current to flow well.
Voltage
 Voltage is a measure of the energy given to the electrons in a
circuit.
 You can say that voltage pushes the electrons round the
circuit.
 The size of a voltage is measured in units called Volts.
 The device used to measure voltage is called a voltmeter.
3
Circuit Symbols
cell
battery
lamp
switch
A
ammeter
V
voltmeter
M
motor
buzzer
resistor
4
Circuits need to be complete for current to
flow
 When the switch is open, there is a gap in the circuit and no
current can flow. The lamp is off.
 When the switch is closed, the circuit is complete, current
can flow and the lamp lights.
Current flows from the negative end of the
battery to the positive end
 Electrons have a negative charge so are attracted to the
positive end of the battery (the “long” end on the symbol)
 The arrows show the movement of the electrons towards
the positive (long) end
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Series circuits
 Connecting things in series is to connect them in one big
loop:
 If there is a gap anywhere in a series circuit, the current
cannot flow.
o So if one lamp breaks, the other one will turn off as well
Parallel circuits
 Connecting things in parallel is to create separate sections,
called parallel branches:
 If there is a gap in a parallel branch, current can still flow in
the other branches.
o So if one lamp breaks, the other lamp stays on
 Adding more lamps in parallel causes the current to increase
and there is no noticeable difference in brightness each time.
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Ammeters and voltmeters
A
V
 Ammeters get connected in series with a component, to
measure the current flowing through a component.
 Voltmeters get connected in parallel with components, to
measure the voltage across a component.
 The voltmeter is measuring the voltage ACROSS the lamp.
Remember:
“Voltage across”
“Current through” (or current “in”)
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Current and voltage for series
 The current is the same at all positions in a series circuit, e.g.
2A
2A
2A
 The voltage of the supply is divided between the
components:
6V
4V
25VV
 The voltage across each component adds up to the voltage
across the supply.
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Current and voltage for parallel
 The sum total of currents in each parallel branch adds up to
the total from the battery, e.g.
6A
6A
2A
1A
3A
 Each separate parallel branch gets the full supply voltage:
6V
6V
6V
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Advantages of parallel
 You can have some components off and some on
o The lights in your house are wired in parallel so that you
can have some on and some off as you choose
 Every separate parallel branch gets the full supply voltage
o Lamps connected in parallel will be brighter than the
same lamps connected in series
 These two lamps can be switched on and off separately
and will light more brightly than if they were connected in
series
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Word List
charge
- everything electrical is said to have charge. For
example, a bolt of lightning is a flow of electric
charge.
positive
- one type of charge, opposite to negative.
negative - one type of charge, opposite to positive.
neutral
- no charge.
electron - a tiny particle which carries negative charge.
current
- a flow of electrons
amperes - the unit used to measure current. e.g. the size of
the current is 9 amperes (abbreviated to 9 A).
ammeter - the device that measures the size of an electric
current.
circuit
- a path for current to flow where components are
connected to a source of electrical energy.
component
- a device used in an electric circuit
cell
- a device that changes chemical energy into
electrical energy.
battery
- a source of electrical energy that is made from
lots of chemical cells.
lamp -
a component that changes electrical energy into
light energy.
switch
- a component that controls the flow of current in a
circuit by making or breaking the circuit.
motor
- a component that changes electrical energy into
kinetic energy.
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buzzer
- a component that changes electrical energy into
sound energy.
conductor - a material which carries electric current. All metals
are conductors.
Insulator - a material which does not allow electric current to
flow.
series
- components are connected in just one loop.
parallel
- separate branches in a circuit.
voltage
- a measure of the energy given to the charges in a
circuit. For example, a 12 Volt supply gives more
energy to the charges than a 3 Volt supply.
volts -
the unit used to measure voltage, e.g. the supply has
a voltage of 12 Volts (abbreviated to 12 V), or the
voltage across the lamp is 6 Volts.
labpack
- a supply of electrical energy where you can change
the voltage. Also known as a variable voltage supply.
voltmeter - a device that measures the voltage across
components.
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