CBSE Class 10 Science Revision Notes Chapter 12
Electricity Class 10 Notes Science Chapter 12:
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CBSE Class 10 Science Revision Notes for the Year 2022-23
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CBSE Class 10 Notes Science Chapter 12
- Electricity was first described using the Greek words “Electrica” and “Elektron”.
- The first person to recognise how certain materials attract other materials when rubbed together was the Greek philosopher Thales.
- Gilbert categorised these materials into two groups, vitreous and resinous, as well as positive charges and negative charges.
- The element that appears first in the series (fur, flannel, wax, glass, cotton, paper, silk, human skin, wood, metals, rubber, resin, amber, sulphur etc ) will gain a positive charge when any two materials in the series are rubbed together, while the element that appears later in the series will gain negative charge.
Fundamental Laws of Electrostatics:
- The two types of charges are positive and negative.
- Similar charges repel one another, but different charges attract one another.
- Coulomb’s Law states that the electrostatic attraction or repulsion force between two charges is proportional to the product of their charges and inversely proportional to the square of their distance.
- F = ( Kq1q2 ) / r2 where K is the constant of proportionality and is equal to 9 x 109 Nm2 / C2 for free space.
- An ebonite rod gets a negative charge when rubbed with fur, while the hair gains a positive charge.
- This demonstrates a transfer of electrons from fur to ebonite.
- The system’s net charge stays the same.
- As a result, charges are transferred from one substance to another rather than being created or destroyed.
Insulators and Conductors:
- Although insulators don’t conduct electricity well, friction can quickly charge them. Example: glass, hard rubber, ebonite etc.
- Although insulators don’t conduct electricity well, friction can quickly charge them. Example: silver, copper, aluminium etc.
- The flow of electric charges is called an electric current, i.e, I = Q / t.
- Ampere is the SI unit of current (A). It is a scalar quantity.
Symbols Used in Electric Circuit:
- Electric circuits are defined as closed-loop current paths.
- A circuit diagram is a diagram that uses conventional component symbols to show how various components in a circuit have been connected.
- The effort required to get a unit positive charge from infinity to a certain place is the definition of the electric potential at that location.
- Mathematically, the electric potential between two points is given as: V = W / Q where V is the potential difference, W is the work done, and Q is the electric charge.
Electric Potential Difference:
- The potential difference between two points is defined as the difference in electric potentials at the two given points. Only when there is a potential difference, also known as a differential in electric pressure, do the electrons move.
- Volts are the SI unit for the electric potential difference.
Electric Potential Energy:
- Electric potential energy is the effort necessary to move charges in opposition to the electric field using a source of energy.
- The potential energy of the charges is used to store the work done.
- According to Ohm’s law, R = V / I. If the potential difference across the two ends of a conductor is 1 V and the current through it is 1 A, then the resistance R, of the conductor is 1 Ω. That is, 1 ohm = 1 volt / 1 ampere.
- The opposition to the passage of current in an electric circuit is measured by the term “resistance.” Ohms are used for measuring resistance. To some extent, all materials are resistive to current flow. Conductors and insulators are the two basic categories into which all materials fall.
- proportionate to the conductor’s length directly.
- directly related to the conductor’s nature.
- directly related to the conductor’s temperature.
- inversely proportional to the conductor’s cross-sectional area.
- Resistivity is the measure of the electrical resistance a substance of unit length and the cross-sectional area provides.
- Resistivity is also known as specific resistance.
- Both a material’s resistance and its resistivity are impacted by temperature.
- The reciprocal of resistivity is called conductivity.
- Ohm-metre is the SI unit for resistivity.
Effect of Temperature:
- The resistance of a conductor rises linearly with temperature.
- The resistance of an insulator increases along with the temperature.
- As temperature rises, a semiconductor’s resistance falls.
- As the temperature rises, an alloy’s resistance rises.
Semiconductors and Superconductors:
- Superconductors are conductors that have no resistance to the flow of current.
- Aluminium, niobium, magnesium diboride, cuprates like yttrium barium copper oxide, and iron pnictides are notable examples of superconductors.
- The resistivity of semiconductors is between that of an insulator and that of a conductor.
Resistances in Series:
- The equivalent resistance of a series of resistors is equal to the sum of their resistances.
- In a series circuit, the current flows continuously throughout the electrical circuit.
- When numerous resistors are connected in series, the combined resistance Rs equals the total of their individual resistances R1, R2 and R3.
- A series circuit’s fundamental drawback is that if one component fails, the entire circuit is destroyed, and none of the other components function.
Resistances in Parallel:
- The reciprocal of the equivalent resistance of a set of resistances connected in parallel is equal to the total of the reciprocals of the individual resistances.
- In a parallel circuit, the potential difference remains the same and the current will vary.
- 1 / RP = 1 / R1 + 1 / R2 + 1 / R3
Heating Effect of Electric Current:
- Heat (H) ∝ square of the current (I).
- H ∝ Resistance of the given circuit.
- H ∝ Time (t) for which current flows through the conductor.
When a potential difference is created, electrons travel, resulting in current flow.
Applications of Heating Effect of Electric Current:
- Electric heating gadgets like electric kettles, irons, geysers, and room heaters all use the heating effect of current to generate heat.
- A fuse wire is a wire that melts, interrupts the circuit, and shields various home equipment from harm.
- It safeguards appliances and circuits by cutting off any excessive electric current flow.
- The gadget and fuse are linked in series.
- Fuse wires are produced using alloys made of aluminium, copper, iron, and lead.
- Work must be done in order to maintain the current flow since there is resistance to the flow of current.
- The energy produced by this work is stored.
- Joules are used as the electrical energy SI unit.
- A kilowatt-hour is the name of the commercial unit of electrical energy (kWh).
- Electric power is the measure of how quickly a task is completed or how quickly electrical energy is used. P = W/t if W is work completed in time t.
- The amount of energy utilised when 1kW of power is used for 1 hour is known as a kilowatt-hour.
Calculation of Power for Household Electricity:
- We calculate the no of units of electricity consumed as; No. of units of electricity consumed in a household = No. of kWh
- The total cost of electricity = Total units × Cost per unit of electricity
- 1kWh = 3,600,000 J.
Class 10 Science Chapter 12 Notes:
What do you mean by the Atomic Structure?
- An atom has a positively charged nucleus that is surrounded by negatively charged electrons.
- Metal valence electrons can freely flow throughout the conductor and produce an electric current.
Definition of Charge:
- The charge is an intrinsic property of matter by virtue of which it can exert electromagnetic force.
FAQs (Frequently Asked Questions)
1. What is an electric circuit?
A channel for transferring electric current is called an electric circuit. It is utilised in numerous electrical gadgets, including computers, motors, and lighting. What does the ‘Ohm’s Law’ state?
2. What does Ohm’s Law state?
Ohm’s Law states that the current through a conductor is proportional to the voltage across the conductor.
3. What is electric power?
The rate, per unit time, at which electrical energy is transferred by an electric current is known as electric power.