RBSE Class 10 Science Notes Chapter 12 Electricity

These comprehensive RBSE Class 10 Science Notes Chapter 12 Electricity will give a brief overview of all the concepts.

RBSE Class 10 Science Chapter 12 Notes Electricity

→ Electric Current – It is defined as the amount of charge flowing through a conductor per unit time. If the charge ‘Q’flows through a conductor in time ‘’ then electric current ‘I’ is given by

I = \(\frac{\mathrm{Q}}{t}\)

The S.I. unit of electric charge is coulomb whose value is equivalent to charge present in 6 × 10¹⁸ electrons. The S.I. unit of electric current is Ampere (A) 1 Ampere is the current flowing through a conductor when one coulomb of charge flowing for one second through a conductor.

→ Electric Circuit – It is a closed conducting path in which different components like cells/battery, ammeter, voltmeter, resistance etc. are attached.

→ Components used in electric circuit

• Cell
• Conductor
• Key switch
• Ammeter
• Voltmeter.

→ An instrument called ammeter measures electric current in a circuit.

→ To set the electrons in motion in an electric circuit, we use a cell or a battery.

→ Electric Potential-Electric potential at a point in an electric field is the ratio of the work done in bringing a unit positive charge from infinity to that point. If W be the work done in bringing a positive charge q from infinity to a point then potential at that point

V = \(\frac{\mathrm{W}}{q}\)

Electric Potential is a scalar quantity and its unit is ‘Volt’.

→ Potential Difference – The electric potential difference between any two points in an electric circuit is defined as the work done in moving a unit charge from one point to other point.

→ Voltmeter – The potential difference is measured by an instrument called “Voltmeter’. Voltmeter is always connected in parallel in an electric circuit.

→ Resistance is a property that resists the flow of electrons in a conductor. It controls the magnitude of the current. The SI unit of resistance is ohm (Ω).

→ Ohm’s Law-It states that the potential difference across the ends of a given metallic
wire in an electric circuit is directly proportional to the current flowing through it, provided its temperature remains constant. V = IR where, R is a constant called resistance of the conductor. Its SI unit is ‘Ohm’. If the potential difference across the ends of 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 = \(\frac{1 \text { Volt }}{1 \text { Ampere }}\)

Volt – If 1 ampere of current is flown through a conducting wire of 1 Ohm resistance, then the potential difference between its two ends is one volt.

→ A component used to regulate current without changing the voltage source is called
variable resistance.

→ In an electric circuit, a device called rheostat is often used to change the resistance in the circuit.

→ Resistance of a uniform metallic conductor is directly proportional to its length (l) and inversely proportional to the area of cross-section (A).

R ∝ \(\frac{1}{\mathrm{~A}}\)
or R = ρ \(\frac{L}{A}\), here

Resistivity or specific resistivity – ρ is a constant called as resistivity of conductor. It is equal to the resistance of a wire of that material of 1 m length and 1 m² area of cross-section. Its SI unit is ohm-meter. Resistivity only depends upon the nature of the matter.
Resistance depends on the nature of material.
Both the resistance and resistivity of a material vary with temperature.

→ Resistance in series-When several resistance is joined in series, the resistance of the combination is equal to the sum of their individual resistance.
R_s = R₁ + R₂ + R₃
When resistance wire are more than three, then
R_s = R₁ + R₂ + R₃ + ……… + R_n

→ Resistance in parallel-The reciprocal of the equivalent resistance of a group of resistances joined in parallel is equal to the sum of the reciprocals of the individual resistance.

When resistance wire are more than three, then

→ Heating effect of electric current-When a potential difference is applied across a.wire by means of a battery, a steady current begins to flow in the circuit due to which it becomes hot. It means the electrical energy is converted into heat energy.

This is called heating effect of electric current. The amount of heat energy produced by an electric current ‘I” in time ‘t’ is given by –
H = VIt.

→ Joule’s heating law-It states that the amount of heat produced in a conductor is

1. directly proportional to the resistance
2. directly proportional to the square of electric current flowing through conductor
3. directly proportional to the time for which the electric current is flowing through it.

Hence, H = I²Rt Joule.

→ Practical examples of heating effect of electric current-Electric heater, electric iron, water heater etc. are the applications of heating effect of electric current.

→ Electric Energy – It is defined as the work done by electrical energy to maintain current in an electric circuit.
Electric Energy E = Vit.

→ Electric Power – The rate at which the electrical energy is dissipated into other forms of energy is called electric power.

Hence, electric power is also defined as the product of electric current and potential difference across wire.

→ Another form of electric power –

P = VI
P= IR × I = I²R = \(\frac{\mathrm{V}^{2}}{\mathrm{R}}\)

The SI unit of electric power is watt (W). It is the power consumed by a device that carries 1A of current when operated at a potential difference of 1 V.

→ The commercial unit of electric power is kilowatt hour (KWh).

1 KWh = 3,600000 J = 3.6 × 10⁶J

→ Kilowatt hour means that when an electric appliance (like heater) works for one hour, then it utilizes one unit electricity.