1. Electric charge Electric charge can be either positive or negative.
COVERED UNDER ELECTRIC CHARGE BY TRIPLE GROUPS ONLY
Electric charge
Electric charge can be either positive or negative.
In an atom an electron has a negative charge that is of the same size as the positive charge of a proton. Neutrons have no electric charge.
As an atom has the same number of electrons as protons it is uncharged.

2. Electric circuits
An electric current will only flow if there is a complete, unbroken electric circuit, that contains a power supply.
A circuit diagram uses a standard set of symbols to show how electrical components are connected together.

3. Circuit symbols
cell
a cell is required to push electrons around a circuit
battery
a battery consists of two or more cells
wire
wires should always been drawn as straight lines
wire junction
switch
a switch enables the current in a circuit to be turned on or off

4. old symbol – the indicator symbol is now used
often a light bulb – this is used to show whether or not a circuit is on
light bulb
old symbol – the indicator symbol is now used A
ammeter
measures electric current in amperes (A) V
voltmeter
measures voltage in volts (V)

5. fixed resistor
a resistor is used to limit the current in a circuit
variable resistor
thermistor
a device whose resistance decreases with temperature
light dependent resistor (LDR)
a device whose resistance decreases with brightness

6. diode
a diode only allows current to flow in one direction (indicated by the arrow)
light emitting diode (LED)
a diode that emits light when it allows the flow of electric current
fuse
a fuse is designed to melt and so break an electric circuit when too much electric current flows
heater
a device used to convert electrical energy to heat

7. The arrow shows the direction of electron flow.
Electric current
An electric current is the rate of flow of electric charge.
An electric current of one ampere (A) flows when a charge of one coulomb (C) passes a point in an electric circuit in one second
In metallic conductors (e.g. copper wire) electrons carry negative charge from the negative side of a power supply, around a circuit and back into the positive side.
The arrow shows the direction of electron flow.

8. In a series circuit Current is the same at any point in the circuit
Do Now
Can you copy this please?
Next draw a parallel circuit with two branches
2.5 A
2.5 A

9. Today’s lesson Looking at current in different circuits
Recall and use: Q = It
Understand that voltage is the number of joules per coulomb transferred
Looking at voltage in different circuits

10. In a parallel circuit
The current splits (total current stays the same)
2.5 A
2.5 A
1.25 A
1.25 A

11. Can you copy this please?
In a parallel circuit
The current splits (total current stays the same)
2.5 A
2.5 A
1.25 A ☺
1.25 A
Can you copy this please?

12. Milliamps - conversions
1 A = 1000 mA
1 mA = ?

13. Milliamps!
1 A = 1000 mA
1 mA = A

14. Electrical conductors and insulators
COVERED UNDER ELECTRIC CHARGE
Electrical conductors and insulators
An electrical conductor is a material through which electric current flows easily.
All metals are conductors.
Electrical insulators have a very high resistance to the flow of electric current.
Complete the table below:
copper
conductor
rubber
insulator
steel
mercury
paper
plastic
diamond
graphite 1 2 3 4 5 6

15. Charge-current equation
electric charge = current x time
Q = I x t
also: I = Q ∕ t
and: t = Q ∕ I
charge
current
time

16. Question 1
Calculate the charge passing through a device when a current of 500mA flows for 3 minutes.
Q = I x t
= 500 mA x 3 minutes
= 0.5A x 180s
charge = 90C

17. Question 2
Calculate the current flowing when a charge of 240C flows through a device in 80s.
I = Q ÷ t
current = 240 C
80s
current = 3A
Now complete the questions on the sheet.

18. Do Now - Please copy and complete Complete:Q I t
60 C
2 A
13 A
5 s
960 C
4 minutes
3 C
50 mA

19. Learning today
Understand that voltage is the number of joules per coulomb transferred
Looking at voltage in different circuits
The definitions of emf and pd
The advantages of connecting bulbs in parallel.

20. Complete: Answers 30 s 65 C 4 A 60 s Q I t 60 C 2 A 13 A 5 s 960 C
4 minutes
3 C
50 mA
30 s
65 C
4 A
60 s

21. Voltage A battery gives electrical charge energy.
The voltage of a battery is equal to the energy in joules provided when a charge of one coulomb passes through the battery.
voltage = energy ÷ charge
1 volt is the same as 1 joule per coulomb

22. Voltage(emf) ☺ V
I’m checking the difference in energy (per coulomb) between the 2 red arrows
1 Volt = 1 Joule per coulomb

23. Voltage (p.d.) ☺
I’m checking the difference in energy (per coulomb) before and after the lamp V
1 Volt = 1 Joule per coulomb

24. Voltage – copy
Voltage V is the amount of energy transferred (changed) per coulomb of charge.
Unit – volts V
It is measured with a voltmeter in parallel
1 volt is the same as 1 joule per coulomb
The unit is named after the scientist Volta famous for making the first batteries

25. Choose appropriate words to fill in the gaps below:
Electric current is the rate of flow of electric _______.
Electric charge is measured in _________.
A battery provides electrical _______ . The amount of energy provided per _________ of electric charge passing is equal to the ________ of the battery.
The _______ supply gives 230 ________ to every coulomb of charge.
charge
coulombs
energy
coulomb
voltage
mains
joules
WORD SELECTION:
coulombs
charge
mains
joules
coulomb
voltage
energy

26. EMF and PD
Electromotive force is please copy the definitions on page 179
Potential difference is

27. EMF and PD both have the volt as a unit
The electromotive force (emf) of a cell or a power supply is the work done per unit of charge by the cell in driving charge around a complete circuit (including the cell itself
The potential difference (PD) across a component is the work done per unit of charge in driving charge through the component.

28. In a series circuit
The sum of the voltages across the lamps equals the voltage across the cells
9 V
3 V
3 V
3 V

29. Can you copy this please?
In a series circuit
The sum of the voltages across the lamps equals the voltage across the cells
9 V ☺
3 V
3 V
3 V
Can you copy this please?

30. In a parallel circuit
In a simple parallel circuit, voltage across each lamp equals the voltage across the cells
5 V
5 V
5 V

31. Can you copy this please?
In a parallel circuit
In a simple parallel circuit, voltage across each lamp equals the voltage across the cells
5 V
5 V ☺
5 V
Can you copy this please?

32. Do Now
Ammeter & Voltmeter

33. Learning today The advantages of connecting bulbs in parallel.
Resistance

34. Electric current flow – conventional current
Electric current flows from the POSITIVE terminal of a power supply around a circuit to the NEGATIVE terminal.
The longer thinner line of the symbol for a cell is the positive terminal.
In the circuit above the diode is aligned so that it allows current to flow through the radio.

35. Series circuits
Circuit components are said to be connected in series if the same electric current passes through each of them in turn. 3A 3A 3A 3A 3A 3A 3A
The cell and the two lamps are in series with each other and so the same electric current passes through all of them.

36. Parallel circuits
The voltage across each component connected in parallel is the same.
The voltmeter reading for component X, V1 will be the same as the voltmeter reading for component Y, V2.

37. In a series circuit all of the components can be controlled by using just one switch.
Each component shares the voltage of the power supply and so adding more bulbs in series will cause each bulb to become dimmer.

38. In a parallel circuit all of the components can be individually controlled by using separate switches.
If one light bulb blows the other bulbs will still carry on working.

39. Exercise
What are the advantages of connecting two lamps in parallel rather than in series to a power supply?
When connected in parallel:
the lamps are brighter than when connected in series
the lamps can be controlled individually with switches
one lamp will continue working even if the other does not

40. Currents in parallel circuits
The total current through the whole circuit is the sum of the currents through the separate components. 5A 5A 3A 3A 2A 2A

41. Calculate the currents measured by ammeters A1, A2 and A3 in the circuit below.

42. Question
Draw a circuit diagram for the torch shown below.

43. Choose appropriate words to fill in the gaps below:
When components are _________ together in series they will all have the same _________ flowing through each of them.
When components are connected in parallel to each other they will each have the same _________.
Lamps are usually connected in __________ to each other as this allows them to be controlled individually by _________ and if one lamp _______ the others can still continue to operate.
connected
current
voltage
parallel
switches
blows
WORD SELECTION:
blows
current
switches
parallel
connected
voltage

44. Online Simulations
Fifty-Fifty Game on Conductors & Insulators - by KT - Microsoft WORD
Signal Circuit - PhET - Why do the lights turn on in a room as soon as you flip a switch? Flip the switch and electrons slowly creep along a wire. The light turns on when the signal reaches it.
Charge flow with resistors in series and parallel - NTNU
Circuit Construction DC Only - PhET - An electronics kit in your computer! Build circuits with resistors, light bulbs, batteries, and switches. Take measurements with the realistic ammeter and voltmeter. View the circuit as a schematic diagram, or switch to a life-like view.
Simple parallel circuit with motor and lamps - Freezeway.com
Simple parallel circuit with motor and lamps and a short circuiting switch - Freezeway.com
Switch quiz circuit - Freezeway.com
Two way switches with a flight of stairs - Freezeway.com
Bulb circuit diagram quiz - Freezeway.com
Hidden Pairs Game Circuit Pairs Quiz basic circuit symbols with this pairs game - by eChalk
Hidden Pairs Game on Circuit Symbols - by KT - Microsoft WORD
Electric Current Quizes - by KT - Microsoft WORD
BBC KS3 Bitesize Revision:
Circuit symbols
Series and parallel circuits
Measuring current and voltage
Current in series circuits
BBC AQA GCSE Bitesize Revision:
Circuit symbols & diagrams
Series & parallel connection
Current & potential difference
Cells and circuits
Series circuits
Parallel circuits

45. Today’s lesson Understand the term power Recall and use: P =VI
Recall and use E = VIt

46. Power
The amount of energy used by a device per second, measured in Watts (Joules per second) A V
Power = voltage x current P = VI

47. Can you copy this please?
Power
The amount of energy used by a device per second, measured in Watts (Joules per second) ☺ A V
Can you copy this please?
Power = voltage x current P = VI

48. Power of a lamp A V Power = voltage x current P = VI
Measure the power of the lamp at it’s operating voltage. What is the electrical energy being turned into? A V
Power = voltage x current P = VI

49. Example
A 200 W television is plugged into the 110V mains. What is the current in the television? P I V X

50. Example
A 200 W television is plugged into the 110V mains. What is the current in the television?
I = P/V = 200/110 = 1.8A P I V X

51. Example
A kettle uses 240V and 8A. What is its power? P I V X

52. P V I Example A kettle uses 240V and 8A. What is its power?
P = VI = 240x8 = 1920W (=1.9kW) P I V X

53. Remember
Power is the amount of energy used by a device per second, measured in Watts (Joules per second) A V
Power = voltage x current P = VI

54. Total energy
So the total energy transformed by a lamp is the power (J/s) times the time the lamp is on for in seconds,
E = VIt
E = energy transformed (J)
V = Voltage (also called p.d.)
I = current (A)
t = time (s)

55. P V I Example A kettle uses 240V and 8A. What is its power?
P = VI = 240x8 = 1920W (=1.9kW)
How much energy does the kettle use in 5 minutes? P I V X

56. P V I Example A kettle uses 240V and 8A. What is its power?
P = VI = 240x8 = 1920W (=1.9kW)
How much energy does the kettle use in 5 minutes?
E = VIt = 240x8x300 = J P I V X

57. Simple!

58. Let’s try some questions!