Electricity can be summarized as follows: 1. Electricity is a type of energy caused by the flow of electrons from negative to positive points. Charge is measured in coulombs and current is the rate of flow of electric charge measured in amperes. 2. Kirchhoff's laws describe the fundamental rules of circuit analysis regarding voltage and current. Ohm's law defines the relationship between voltage, current, and resistance in circuits. 3. There are different types of circuits including series, parallel and combinations. Components behave differently depending on the circuit type regarding voltage and current.

1. Electricity
BY RAJESH J

2. What is Electricity
 A type of energy fuelled by the transfer of electrons from negative to
positive points within a conductor.

3. Electrical Charge
 Electric charge is given the symbol
Q
Electrons are the charge carriers that flow in an electrical circuit from the
negative to positive terminals.

4.  Charge is measured in
Coulombs
 which is given the symbol
C

5. Current
 An electric current is a rate of flow of electric charge. In electric circuits this
charge is often carried by moving electrons in a wire.
Denoted with letter “ I “
Units: Amperes (A)

6. Kirchhoff's Current Law
 The sum of all the currents into a junction is the same as the sum of all the
currents out of that junction.
Or
The algebraic sum of all the currents entering and leaving a node is
equal to zero

7. Voltage
 Energy applied per unit charge is called voltage.
V=
𝐸
𝑄
Where V = Voltage in Volts
E = Energy applied by source ( ex: battery) in Joules
Q = Total Charge in Coulomb

8. Kirchhoff's Voltage Law
 The sum of input voltage is equal to sum of voltage drops in a loop.
or
 Th e algebraic sum of all the voltages in a loop is equal to zero.

9. Circuit Symbols

10. Electrical Circuits

11. Different types of circuit
There are different ways in which you can connect cells and components
(such as lamps) to create a circuit:
 series
 parallel
 combination of both

12. Series Circuit
 A series circuit has only one electrical path.
 You can trace from one side of the battery to the other, through each
component, without lifting your finger from the page.

13. Current and Voltage in Series
 Current remains same in series circuit.
 Voltage gets divided.

14. Question:
 Build a series circuit which contains a 6V battery pack, three 2 V lamps in
lamp holders, and a meter used for measuring current.
 What is the meter called?
 Where is it positioned in the circuit?

15. Quiz
 What is a series circuit?
 What is the symbol for current?
 What are the units of current?
 What is the relationship between current and time?
 What do we know about the current in a series circuit?
 How do we measure current?
 Draw the symbol for this.
 Describe how to measure current in a series circuit.

16. Parallel Circuit
 In a parallel circuit, all components are connected across each other,
forming exactly two sets of electrically common points.

17. Current and Voltage in Parallel
 Voltage remains same in parallel circuit.
 Current gets divided.

18. Question:
 Build a parallel circuit which contains a 6V battery pack, three 6V lamps in
lamp holders, and a meter used for measuring total current and to
measure the voltage across each lamp
 What is the meter called to measure voltage?
 Where is it positioned in the circuit?

19. Quiz
 What is a parallel circuit?
 What is the symbol for voltage?
 What are the units of voltage?
 What do we know about the voltage in a parallel circuit?
 How do we measure voltage?
 Draw the symbol for that measuring instrument.
 Describe how to measure voltage in a parallel circuit.

20. Combination of Series & Parallel

21. Resistance
Electrical resistance, the measure of the degree to which a conductor opposes an electric current
through that conductor
Resistance is denoted with R
Units: ohms Ω

22. Resistivity of Some Materials

23. Ohm’s Law
 The potential difference (voltage) across an ideal conductor is proportional
to the current through it. The constant of proportionality is called the
"resistance", R.
 Ohm's Law is given by: V = I R
(where V is the potential difference between two points which include a resistance R).
 Therefore, R =
𝑽
𝑰

24. Ohmic Resistors
 Ohmic resistors are those resistors that have a constant resistance. In other words, the follow the
Ohm's law.
 If you take such a resistor, apply voltage across it, whilst measuring current and voltage, and then
draw a graph of current versus voltage, you get a straight line
 Example: wire
 Note: Many electrical components in today's
electronics do not follow Ohm's law.

25. Non-Ohmic Resistors
 Non-Ohmic Resistors gives a curve with an increasing gradient. It shows
that the resistance increases as the current increases.

26. Examples of Non Ohmic Resistors
Filament Bulb

27. Examples of Non Ohmic Resistors
 A diode only allows current to flow in one direction through it (forward biased), when the
current tries to flow the other way (reverse biased) no current is allowed to flow through the
diode.
Diode

28. Examples of Non Ohmic Resistors
 The resistance of a thermistor decreases as it’s temperature increases.
 the thermistor is used in circuits which monitor and control the temperature of rooms,
freezers & fridges etc.
Thermistor

29. Examples of Non Ohmic Resistors
 The resistance of an LDR decreases as the light intensity falling on it increases.
 LDR’s are used in circuits which automatically switch on lights when it gets dark, for example
street lighting.
LDR (light dependent resistor)

30. Super Conductors
 A superconductor is a material that can conduct electricity with no
resistance once they are cooled to a temperature called the transition
temperature Tc.
For Example :
Transition Temperature for 1. Mercury is 4 Kelvin
2. Calcium is 254 Kelvin
Application: maglev trains, magnetic resonance imaging (MRI)

31. Applications of Super Conductor
 Most train magnets are also electromagnets, often using liquid nitrogen-cooled superconductors to
lower the energy required to create such large fields
 Magnets made from rare-earth elements, however, produce a stronger magnetic field than ferrite
(iron compounds) or alnico (alloys of iron, aluminium, nickel, cobalt, and copper) magnets to lift and
guide the train cars over a guideway.
Maglev Train

32. Applications of Super Conductor
MRI

33. Equivalent Resistance

34. Problems from the text book
pg no:49

35. Electronic Circuits and Devices
Voltage Divider
A voltage divider is a simple circuit which turns a large voltage into a
smaller one.

36. Problem from text book pg 53

37. Capacitors
 A capacitor (originally known as a condenser) is an electrical component
used to store energy electrostatically in an electric field.
 It contains two electrical conductors (plates) separated by a dielectric (i.e.,
insulator).
 Applications:
DC blocking capacitor
Capacitor as a filter : Low pass filter and High pass filter

38. Capacitance (not in syllabus)
Note : Permittivity of Vacuum is 8.85 x 10-12 farad per meter (F/m)

39. Diode
 A diode is a specialized electronic component with two electrodes called the anode and the
cathode. Most diodes are made with semiconductor materials such as silicon, germanium, or
selenium.
 The fundamental property of a diode is its tendency to conduct electric current in only one
direction.
Note: If Anode of Diode is connected to anode and Cathode of Diode is
connected to cathode of Voltage source respectively, then diode is said
to be Forward biased i.e acts as ON Switch.
But, If reverse polarities connected called Reverse biased i.e acts
a OFF Switch

40. Applications of Diode
Half Wave Rectifier:

41. Applications of Diode
Full Wave Rectifier [type 1]

42. Applications of Diode
Full Wave Rectifier [type 2]

43. Problems based on KCL, KVL and Ohm’s Law
 Required : Kirchhoff’s Laws, Ohm’s Law and Simultaneous Equations (Maths)

44. Problems based on KCL, KVL and Ohm’s Law
 Find current in each resistor.

45. Problems based on KCL, KVL and Ohm’s Law
 If B1= 20 volts, B2 = 10 volts; R1, R3, R5 = 5 ohms; and R2, R4 = 2 ohms. Find current in each
resistors.

46. Problems based on KCL, KVL and Ohm’s Law
 Find the current flowing through R5 with proper direction.

47. Problems based on equivalent resistance

48. Problems based on equivalent resistance

49. Problems based on equivalent resistance

50. Problems based on equivalent resistance

51. Logic Gates (Not in Syllabus)

52. Truth Table

53. Two Way Switch

54. Static Electricity
 When two objects are rubbed together to create static
electricity
 One object gives up electrons and becomes more
positively charged while the other material collects
electrons and becomes more negatively charged.
 This is because one material has weakly bound electrons,
and the other has many vacancies in its outer electron
shells.
 One common example of this would be shuffling your
feet across carpet.

55. Electricity Completed

56. Next Chapter:
Electromagnetism

57. Bibliography
 http://physicsnet.co.uk/gcse-physics/non-ohmic-devices/
 http://whatis.techtarget.com/definition/diode
 http://www.ee.surrey.ac.uk/Projects/CAL/digital-logic/gatesfunc/