class 10th Physics Electricity important points

class 10th Physics Electricity important points

https://cbsenotesallsub.blogspot.com/2023/12/class 10th physics Electricity important points.html 

class 10th Physics by Daksh amit sir  

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ch-  Electricity 

Charge 

• charge = Number of electron x e

• Q = ne

• n= q/e         where  Q= charge

•  n = number of electrons

•  e =  1.6 x 10 to the power mines 19

• SI unit of charge is couloumb.

• 1 coulomb charge have 6.25x10 to the power 18 electrons

• Like charge always repel to each other.

• Unlike charge always attract to each other.

• Those substances by which electricity can flow are known as conductors Eg Silver, Copper, Aluminum, Nichrome, Graphite, Mercury, Manganin wet  wood etc.

• Those  Substances by which electricity can not flow are called  insulators 
• Eg sulpher,cotton, air, paper ,mica, bakelite,polythene ,plastic, dry wood etc

• The presence  of free electrons in a metals make it a conductor

• There are no free electrons in an insulator.

• Insulator does not allows the flow of electric charge.

Electric Potential 

• 1Volt = 1J/1C

• Joule / Coulomb is also called Volt

• Voltmeter is used for measuring the P.D.

• The meaning of P.D. is  Potential Difference

• Potential difference = work done/ charge

• v = w/ Q     unit  is volt or joule /coulomb

• Voltmeter always connected in parallel in  a circuit because it have higher resistance.

• Electric potential at a point is 1 Volt means 1 joule of work is done in moving 1 unit positive charge from infinity to that point.

• Potential difference between two points in an electric circuit is defined as the amount of work done in moving a 1 coulomb charge from one point to the other point.

• Voltmeter is used for Measure the potential difference between two points.

• Voltmeter is always connected in parallel across two points where the potential difference  to be measured.

• voltmeter has a higher resistance so that takes a negligible current from the circuit.

Electric current

• Rate of flow of charge is called electric current.

• current = charge / time

• I = Q/t

• SI unit of current is Ampere.

• 1 Ampere = 1 coulomb / 1 second

• Electrons actually travels through the wire when switch on a light.

• Electric current is measured by Ammeter.

• Ammeter is connected in series in a circuit because it have low resistance.

• The resistance of an Ammeter is very small so that it may not change the value of the current flowing in the circuit.

• The resistance of a voltmeter is very large so that it take negligible current from the circuit.

• Conventional direction of flow of electric current is from positive to negative terminal through  the outer circuit.

• The direction of flow of electrons is opposite to the direction of flow of current. means from Negative terminal to positive terminal.

Ohm's Law

According to Ohm's Law  The voltage across a conductor is directly proportional to the current flowing through it at constant temperature.

• According to Ohm's Law  V∝ I

• V =I R      where  R = Resistance  R = V/ I

• Unit of resistance is Ohm , it is denoted by  Ω

• An insulators have infinity high electrical resistance 

• The current is directly Proportional to potential difference.

• I ∝ V

• The current is inversely proportional to the resistance .

• I ∝ 1/ R

• According to the formula  I = V/R  if resistance  is doubled then current will be halved

• If  resistance is half the current will be doubled.

• If the  potential difference is halved ,then the current also halved.

• If the potential  difference is doubled ,then the current also doubled.

• Ohms law is valid only if temperature remains constant.

• Voltage and current graph according to ohms law is always a straight line graph

RESISTANCE 

• Resistance of the wire is directly proportional to the length of the wire   

• R ∝ L 

• Resistance of the wire is inversely proportional to the cross sectional area of the wire.

• R  ∝ 1/A
• if  R ∝ L  ,R ∝ 1/A   ,then R ∝ L/A  , R = σ L/ A 

            Where  σ = Resistivity of the Wire

• If length of the wire is double then resistance will be also doubled

• If length of the wire is half then resistance will be also halved.

• If the cross sectional area of the wire is double then the resistance of the wire will be halved

• If the cross sectional area of the wire is half then resistance of the wire will be doubled.   

• If the diameter of the wire is double then the resistance of that wire will be one fourth.

• If the diameter of the wire is half then the resistance of that wire will be four times       

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combination of  Resistance

• There are mainly two types of combination  in resistance

1. Series Combination
2. Parallel Combination

one more combination  mix combination in  which both series and parallel combination  are used.

Series Combination

   R =  R1 +R2 +R3

• In series combination two or more resistance are connected end two end 

• In series combination second  end of the first resistance is connect to the first end of the second resistance.

• In series combination current is same in each  resistances.

• In series combination voltage is different in each resistances.

Parallel combination

1/R = 1/R1 + 1/R2 + 1/R3

• In parallel combination one end of each resistance is connected with one point  and other end of each resistance is connected with other point. 

• In parallel combination each  resistance  have same voltage.

• In parallel combination each resistance have different current.

• In case of parallel combination the resultant resistance will be less than either of the individual resistances.

• If a wire has resistance R is cut in  two equal parts, then each parts of the wire  having resistance  half   ie. R/2 

• Lights in our houses are wired in parallel combination.

• Each electrical appliance have same voltage in parallel combination.

Electric Power

• work done per unit time is called electric power, power is denoted by 'p'

• Electric Power = work done /time  taken

• P = W/T

• SI unit of Power is watt.

• Electric Power is also defined as the electrical energy consumed per unit time

• Power = Electrical Energy / Time

• P = E/T
• When one joule energy is used for one second then electrical power is equal to one watt

unit of power is - watt