Electricity ppt for class 10

Class 10 cbse Electricity ppt

1. Science Formative assessment 1 Submitted by : Guided By : Prasann Jaiswal Shweta Sood Ma’am Rohan Sharma Dipti Matta Deepank Agrawal Ritik Rathore Electricity 2015-16

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. P arallel 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 : Positive Charge (Due to electron deficiency) 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 .

6. Electroscope

7. Properties Of Charge 2 .

8. 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

9. Methods of Charging 3 .

10. Methods of C harging 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.

11. Methods of C harging 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.

12. What is Electricity ? 4 .

13. 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.

14. Electric Current 5 .

15. 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

16. Electric Field 6 .

17. 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

18. Electric Potential and 7 . Potential Difference

19. 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)

20. 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 .

21. Ohm’s Law 8 .

22. 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 - Ohmic conductors (follow ohm’s law) Non- ohmic conductors (do not follow ohm’s law)

23. I-V Graphs for Conductors

24. Resistance and Resistivity 9 .

25. 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

26. 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 = ρ l/A where constant “ ρ ” is the specific resistance of the conductor

27. 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 m 2 then R = ρ It depends on material of the conductor Denoted by rho i.e. “ ρ ” S.I. unit is Ohm metre ( Ω m) Ρ α Temperature of the conductor Also known as R esistivity

28. Resistivity Table

29. 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

30. Electric Circuit and 10. Its Components

31. 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

32. Measuring Devices 11.

33. 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.

34. 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 .

35. Combination of Resistances 12 .

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

37. 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

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

39. 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 . D ifferent 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.

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

41. Series Vs. 13. Parallel

42. 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.

43. THANK YOU