Electricity | Class 10th Science | CBSE Notes | Study World

Electricity || Class 10th Science || CBSE Notes || Study World

Hello Everyone, Today we are providing the CBSE Notes of Class 10 Science Chapter- Electricity. These notes are prepared by experienced teacher as per the latest syllabus. These notes are helpful for the students of 10 Class.  

👉 Topic in the Chapter

• Introduction
• Charge
• Conductors
• Resistors
• Insulators
• Principle of Conservation of Charge
• Coulomb's Law of Electricity
• Dielectric Constant
• Electrostatic Potential
• Potential Difference
• Volt 
• Voltmeter 
• Electric Current
• Ammeter
• Electric Current
• Ohm's Law
• Experimental Verification of Ohm's Law
• Resistance
• Factor on which the resistance of a conductor depend.
• Factor on which Electric Current following through a conductor depend
• Resistivity
• Super Conductivity
• Combination of Resistance in series
• Combination of Resistance in parallel
• Law of Combination of Resistance in parallel
• Electric Power
• Effect produced by Electric Current
• Application of Heating Effect of Electric Current. 
• Joule's Law of Heating.

Charge: It is the deficiency or excess of electron on a body.

It is a scalar quantity and is measured in coulomb (c).

Types : It is of two type:

Positive charge (+ve) and Negative charge(-ve).

👉 Like charge repel each other and unlike charges attract  each other.

Charge on one Electron: 1.6 × 10 ^{– 19} Coulombs.

Static Electricity: It is the study of charge at rest.

Current Electricity :-  It is the study of charge in motion.

Conductor: These are the substance which have negligible electric resistance and hence allow the electric current to pass through them freely. E.g. metal like Iron, copper, aluminium, silver, etc.

Resistors: These are the substance which have comparatively high electric resistance then conductors  and hence do not allow the electric current to pass through them freely. E.g. alloy like Nickrome, Constanton, Magnesium etc.

Insulator: These are the substance which have infinitely high electric resistance and do not allow electricity to pass through them at all. E.g. wood, plastic rubber, etc.

Principle of Conservation of Charge

According to this principle, the total electric charge in an isolated system always  remain conserved. i.e. it can neither be created nor destroyed.

Coulomb's  Law of Electricity

According to this law “ The force of attraction or repulsion between any two charge is directly proportional to the product of the quantity of charge and is inversely proportional to the square of distance between their centre.

Mathematically: If q₁ and q₂  be the two charge separated by distance r 

 where K is dielectric constant. 

Dielectric Constant: 

So dielectric constant is numerically equal to the force of attraction or repulsion between two charges each of IC separated by a distance of 1 metre.

SI unit of Dielectric Constant.

Electrostatic Potential: Electrostatic potential at a point is define as the amount of work done in bringing a unit positive charge from infinity to that point.

Potential  difference: Potential difference between two point in an electric field is defined as the amount of work done in moving/ bringing a unit +ve charge from one point to another.

Mathematically:

 It is denoted by V and is a scalar quantity and is measured in volt by voltmeter.

SI unit of Potential difference :

Volt: Pressure difference between two point in an electric field is said to be 1 Volt if one joule of work is done in transferring a charge of one column.

Voltmeter: It is a device used to measure the potential difference across the end of the conductor. It is high electric resistance and is always connected in parallel.

Electric current: It is the flow of electric charge i.e.  electron in a conductor.

Mathematically:   I = Q / T

S.I. Unit of electric current is Ampere.

1 A = 1 Coulomb÷ 1 Sec

1 Ampere : If 1 column of charge flow through a conductor at any point in 1 second then the electric current is 1 Ampere.

Ammeter: It is a device which is used to measure the electric current flowing through the conductor. It is low electric resistance and always connected in series as shown in figure above.

Electric Current: It is the closed and continuous path consisting of connecting wires and other resistance all connected in between the two terminals of the battery through which the electric current flow.

Ohm’s Law: According to  Ohm’s Law “at constant temperature the current flowing through a conductor is directly proportional to the potential difference across the ends"

Mathamatically: 

           

Where   is a constant and is known as Resistance of the conductor.

Experimental Verification: 

Apparatus required: A conductor XY of resistance R for which Ohm’s Law is to be verified. Voltmeter, Ammeter, Battery, Key Rehostat (Rh) and connecting wires.

Procedure: Set the mentioned apparatus as shown in figure. Now the current in the circuit is verified by adjusting the resistance of rehostat.

For each value of current I in Ammeter, there is a corresponding value of Potential difference in voltmeter is recorded and each time it is found that the ratio is plotted then a straight line is obtained which further verifies Ohm's Law.

when a graph between V and I is plotted then a straight line is obtained, which further verifies Ohm's Law

Resistance: The opposition offered in the flow of electric current is known as resistance.

Mathematically: It is a constant and is defined as the ratio of potential difference across the end of the conductor to the current flowing through it.

It is denoted by R, is a scalar quantity and is measured in Ohm (Ω)

S.I. unit of Resistance:-

1 Ohm = If on applying a potential difference of 1 volts across the ends of a conductor, a current of 1 ampere flows through it, then its resistance is said to be 1 Ω

Factors on which the resistance of a conductor depend upon:-

Following are the factor on which the resistance of a conductor depend upon :

Length of the conductor: The resistance of a conductor is directly proportional to the length of conductor.i.e. R ∝ L

This mean if the length of the conductor increases then its Resistance will also increase.

Area of the cross section:- The resistance of a conductor is inversely proportional to the area of cross section i.e. thickness. i.e. R ∝ 1/A

It mean greater the area of the cross section of a wire lesser will be the resistance.

Temperature of the Conductor: The resistance of a conductor is also depend upon the temperature of the conductor.In fact, it is also directly proportional to the temperature. i.e. R ∝ T  

It mean greater the temperature greater will be the resistance.

Nature of the material of the conductor: Resitance of the conductor is also depend upon the nature of the material of the conductor.

Factor on which Electric Current flowing through a conductor depend upon:

As we know that according to Ohm’s law :

It mean the current flowing through a conductor is directly proportional to the potential difference and inversely proportional to the resistance of the conductor. i.e. if voltage increase current also increase.  And  if resistance increased then a current decrease.  

 Resistivity : Since we know that 

Where  ρ(Rho) is a constant and is known as resistivity of the conductor its value depend on the nature of material of the conductor.   

Now 

So resistivity of a substance is numerically equals to its resistance which is taken in the form of rod whose area of cross section is 1 metre square and length one metre.

SI unit of Resistivity

 Smallest unit of current is mili Ampere

1 mA = 10 ^-3   A or 0.001 A

Super Conductivity : It is the phenomena of loss of an electric resistance by a metal when it cooled to an extremely low temperature to become a superconductor.

Transition Temperature: It is a minimum temperature at which a metal become a superconductor. E.g. The transition temperature of mercury is – 269 degree Celsius.

Combination of Resistance

Resistance can be combined into ways:-

(1) In series

(2) In parallel

Combination of Resistance in Series:-

When two or more resistance are joined end to end consequently then they are said to be connected in series.

Law of Combination of Resistance in Series:-

The equivalent resistance of any number of resistance in series is equal to the sum of individual resistance. i.e.

                                                      R =  R1 + R2 + R3

where R is resultant resistance and R1 + R2 + R3 ........Rn be the individual resistance

Relation for the Equivalent Resistance of three Resistance in Series

Consider three resistance R1 ,R2, R3 are joined in series to a battery of V Volts as shown in figure.

Let R be the equivalent resistance and I be the current flowing through the circuit.

Also Let V1 , V2, and V3 be the potential difference across R1 , R2, R3 respectively. 

Apply Ohm’s  Law :  For whole circuit  V =I R

                   For R1                   V = I R1

                   For  R2                  V2 = I R2

                    For  R3                  V3  = I R 3

                    As  V = V1 + V2 + V3

                     I R = IR1 + IR2 + IR3

                     IR = I(R1 + R2 + R3)

                      R = R1 + R2 + R3

Combination of Resistance in Parallel :

When two or more resistance are joined between the same two points then they are said to be connected in parallel.

Law of combination of Resistance in Parallel

The reciprocal of equivalent resistance of any number of resistance in parallel is equal to the sum of reciprocal of the individual resistance
i.e. 

Relation for the Equivalent Resistance of three resistance in Parallel.

Consider three resistance R1 R2 R3 are joined in parallel to a battery of V Volts.

Let R be the equivalent resistance and I be the current flowing through the circuit.

Also Let I1 I2 and I3 be the current flowing through R1 R2 R3 respectively.

Now apply Ohm’s  Law.

Electric Power :- It is defined as the rate at which the electric work is done by an appliances.

 or

It is defined as the rate at which electric energy is consumed by an appliance.

Mathematically:

It is denoted by P and is a Scalar quantity and is measured in watt.

S.I.Unit of Electric Power:-

1 Watt :- Power of an appliance is said to be 1 Watt if 1 Joule of work is done by it in 1 second

 Or

If  1 Joule of electric charge are consumed by it in 1 second.

Other Units of Electric Power

Kilowatt :  1 Kw = 10³ watt

Megawatt : 1 MW = 10⁶ watt

Horse Power: 1 HP = 746 watt

Formula for calculating Electric Power

 Since we know that 

Formula for calculating Electric Energy  Consumed

 E = Pt

Commercial/trade Unit of electric energy consumed is Killowatt hour.[kwh]

Killowatt Hour:- 1 kwh is that amount of electrical energy consumed by it if its Power is 1 Kw and it is used for 1 hour.
1 Kwh = 1000 W/ h
1 Kwh  = 1000 J/ S ❌  3600 S = 3600000 J = 3•6 ✖️  10⁶  J

Effective produced by Electric Current :-An electric Currentproduced three most important effects

(1) Heating effect

(2) Chemical effect

(3) Magnetic effect

Heating effect of Current :- When an electric current is passed through a high resistance wire like nichrome, it become very hot and produce heat.

This is called the heating effect of electric current.

This is effect is obtained by the transformation of electric energy into heat energy.

Thus the rate of resistance is same as the role played by friction in mechanism.

Application of Heating Effect of Electric Current.

(1) It is used in electrical heating appliances such as electric heater, oven, toaster, geyser, electric iron,etc.

(2) It is used in electric bulb for producing light.

(3) An electric fuse is also an appliance of heating effect of current.

Joule's Law of Heating

Since we know that W = V Q 

                      ⇒  W = (IR) (It)     [ ∵ V = IR   Q = It ]

                    ⇒  W =  I² Rt

Assuming that all the work done by the appliance is converted into Heat energy.

So above equation can be written as H =  I² Rt

Where     H=Heat produced in Joule.

                  I = Electric current in Ampere

                   R = Resistance of conductor in Ohm

                   T =time.

Conclusion :- H ∝   I²   , H  ∝ R  , H ∝ t