Class 10 cbse Electricity ppt

1. Submitted by : Guided By :
Prasann Jaiswal Shweta Sood Ma’am
Rohan Sharma
Dipti Matta
Deepank Agrawal
Ritik Rathore
Electricity

2. ELECRICITY

3. Contents
 What is Charge ?
 Properties of Charge
 Methods of Charging
 What is Electricity ?
 Electric Current
 Electric Field
 Electric Potential & Potential Difference
 Ohm’s Law
 Resistance
 Electric Circuit and components
 Current and Voltage Measurements
 Combination of Resistances
 Series vs. Parallel
NOTE-Direction of CONVENTIONAL Current is opposite to direction of flow of electrons.

4. What is
a Charge ?
1.

5. What is a Charge ?
• Charge is the inherent property of matter that feels force
of attraction out repulsion due to excess or deficiency of
electrons.
• It is of 2 types :
A. Positive Charge (Due to electron deficiency)
B. Negative Charge (Due to excess of electrons)
• Its S.I. unit is Coulombs denoted by ‘C’.
• It is detected and measured using a device called
Electroscope.

7. Electroscope

8. Properties2.

9. Properties of Charge
• The total charge of the universe is conserved i.e. constant
• Like Charges attract each other and unlike charges repel
each other
• Charges are additive in nature
• Charges are always quantized i.e. Q = n x e
where q = charge,
n = no. of electrons
e = charge on one electron i.e. 1.67 x 10-19 C
• Charge is relativistically constant

10. Methods
Charging
3.

11. Methods of Charging
• Charging by Conduction
When an uncharged body is brought into contact
(touched) with an charged body then the charge or
electrons are transferred from the charged body to the
uncharged body. This charges the uncharged body.

12. Methods of Charging
• Charging by Induction
In the induction process, a charged object is brought
near but not touched to a neutral conducting object.
The presence of a charged object near a neutral
conductor will polarize the charge within the
conductor.

13. What is
Electricity ?
4.

14. What is Electricity ?
• Electricity is a form of a energy that can be easily
changed to many other forms.
• It can also be defined as flow of electrons in a
circuit.

15. Electric5.

16. Electric Current
• It is the rate of flow of electric charge (or electrons)
through a conductor i.e.
I = Q/t = ne/t where I stands for current
• It is a scalar quantity
• Its S.I. unit is coulomb per second or amperes (A)
• It is measured by a device called Ammeter
• Its direction is taken opposite to the flow of electrons
• It flows as a result of potential difference across the
ends of a conductor

17. Electric
6.

18. Electric Field
• It is the 3 dimensional space around a charge in
which the force of attraction or repulsion can be felt.
Electric Field Intensity
• It is the force experienced by a unit positive charge
when placed in a magnetic field
• It is denoted by ‘E’
• Its S.I. unit is newton per coulomb (N/C)
• It is a vector quantity

19. Electric Potential
and
7.
Potential Difference

20. Electric Potential
• It is the amount of work done in bringing a unit
positive charge from infinity to a given point in the
electric field.
• It is a scalar quantity
• Its S.I. unit is joules per coulomb or volts (V)

21. Potential Difference
• It is the amount of work done in bringing a unit positive
charge from one point to another point in an electric field.
• It is a scalar quantity
• Its S.I. unit is joules per coulomb or volts (V)
• It is responsible for the flow of current in a conductor.
• Measured by a device called Voltmeter.
.∞
B. A.

22. Ohm’s8.

23. Ohm’s Law
• It was stated by Georg Simon Ohm
• It states that at constant physical conditions like temperature
are kept constant then the amount of current flowing
through a conductor is directly proportional to the potential
difference across its ends i.e.
I α V
V = IR where R is constant called Resistance
• According to this law conductors are divide into -
1. Ohmic conductors (follow ohm’s law)
2. Non- ohmic conductors (do not follow ohm’s law)

24. I-V Graphs for Conductors

25. Resistance
Resistivity
9.

26. Resistance
• It is defined as the hindrance to the flow of current
• It is the ratio of potential difference to current i.e.
R = V/I
• Its S.I. unit is volts per ampere or Ohm (denoted by Ω)
• Reciprocal or resistance is called Conductance (C) .
S.I. unit Ohm-1 i.e. Ω-1

27. Factors affecting Resistance
• R α Length (l) ……(i)
• R α 1/Area of cross section of conductor (A) ………(ii)
From (i), (ii) and (iii) we get
 R α l/A
 R = ρl/A where constant “ρ” is the specific resistance of the
conductor

28. Specific Resistance
• Specific resistance is the resistance of a conductor of unit
length and unit cross sectional area i.e.
if l = 1 m and A = 1 m2 then R = ρ
• It depends on material of the conductor
• Denoted by rho i.e. “ρ”
• S.I. unit is Ohm metre (Ωm)
• Ρ α Temperature of the conductor
• Also known as Resistivity

29. Resistivity Table

30. Fixed Resistors Variable resistance or Rheostat
Types of Resistances
 Fixed Resistances: Their value does not change under
constant physical conditions. They are set at a particular
value
 Variable Resistances: Their resistance can be easily
changed by changing area of cross section and length

31. Electric Circuit
and
10.
Its Components

32. Electric Circuit
• A closed path in which electric current can flow is called an
electric circuit
• There are 2 types of circuits –
1. Open Circuit: No current flows
2. Closed Circuit: Current flows continuously
Open
circuit
Closed
circuit

34. Measuring11.

35. Ammeter
 It must be connected in series in the circuit.
 Positive side of ammeter must be connected nearest
to the positive terminal of the battery (electric cell),
and vice versa.

36. Voltmeter
 Voltmeters must be connected in parallel to the
circuit.
 The positive side of voltmeter is connected to the
positive terminal of the cell, and vice versa.

37. Combination
Resistances
12.

38. Combination of Resistances
There are 2 ways of joining resistors together
1. Series Combination
2. Parallel Combination

39. Resistance in Series
• When two (or more) resistors are connected end to end
consecutively, they are said to be connected in series.
• When a number of resistors connected in series are joined
to the terminal of a battery, then each resistance has a
different potential difference across its ends (which
depends on the value of resistance). But the total
potential difference across all the ends of all the resistors
in series is equal.
• When a number of resistors are connected in series, then
the same current flows through each resistance

40. Resistance in Series
• The figure shows three resistances R1,R2,R3 connected in series. Now
suppose potential difference across resistance R1 is V1 , R2 is V2 and
R3 is V3. Let potential difference across battery be V, then :
V = V1+V2+V3.
Applying Ohm’s law to the whole circuit : V = IR. ………..(1)
Applying Ohm’s law to the three resistors separately, we get:
V1 = I x R1. ………………….. (2)
V2 = I x R2. ………………….. (3)
V3 = I x R3. ………………….. (4)
Substituting (2), (3), (4) in (1)
IR = IR1 + IR2+ IR3
OR, IR= I (R1+R2+R3)
Or, R = R1+R2+R3 .
Therefore we conclude that the sum total resistance in a series resistance
connection is equal to the sum of all the resistances.

41. Resistance in Parallel
• When two (or more) resistors are connected between the same
points, they are said to be connected in parallel.
• When a number of resistance are connected in parallel, then the
potential difference across each resistance is same which is equal
to the voltage of battery applied.
• Different amounts of current flows through each resistance (which
depend on the value of resistance). But the current flowing through
each parallel resistance, taken together, is equal to the current
flowing in the circuit as a whole. Thus, when a number of
resistance are connected in parallel, then the sum of current
flowing through all the resistances is equal to the total current
flowing in the circuit.

42. Resistance in Parallel
• The figure shows three resistances R1,R2,R3 connected in series. Now
suppose currant across resistance R1 is I1 , R2 is I2 and R3 is I3. Let
total current in the circuit be I, then:
I = I1+I2+I3.
Applying Ohm’s law to the whole circuit : I = V/R. ………..(1)
Applying Ohm’s law to the three resistors separately, we get:
I1 = V / R1. ………………….. (2)
I2 = V / R2. ………………….. (3)
I3 = V / R3. ………………….. (4)
Substituting (2), (3), (4) in (1)
V/R = V/R1 + V/R2+ V/R3
OR, V/R= V (1/R1 +1/R2 + 1/R3)
Or, 1/R = 1/R1+1/R2+1/R3 .
Therefore we conclude that the sum total resistance in a parallel
resistance connection is equal to the sum of reciprocal of all the
resistances.

43. Series
Vs.
13.
Parallel

44. Series vs. Parallel
S.No. Criteria Series Parallel
1.
Equivalent
Resistance
More than the highest
resistor
Less than or equal to the
lowest resistor
2.
Amount of Current Current is less as
resistance is more
Current is more as resistance
is more
3. Switching on/off
If one is appliance is
switched off others also do
not work
If one is appliance is
switched off others work
independently
4. Appliance failure
If one appliance stops
working, none of the
appliances will work
If one appliance stops
working, others will work
independently
5.
Potential
Difference
Each appliance receives
maximum potential
difference
Potential Difference is
divided so, each appliance
receives less P.D.