**Electricity** is an important topic in **Class 10 Science**, and it's essential to have a good understanding of the concepts to do well in exams. These **simplified notes** cover the key topics in electricity, including electric current, circuits, Ohm's law, Series connenction, Parallel connection, Heating effect, and Power making it **easy to revise** and prepare for your exams.

Subject | Science (Physics) |

Class | 10 |

Board | CBSE |

Chapter No. | 11 |

Chapter Name | Electricity |

Type | Notes |

Session | 2024-25 |

"Success is not how high you have climbed, but how you make a positive difference to the world."- Roy T. Bennett

**Electricity Class 10 Notes: A Comprehensive Guide for Class 10 Students**

## Table of Contents

**Electric Current and Circuit**

- If the electric charge flows through a conductor, we say that there is an electric current in the conductor.
- Electric current is expressed by the amount of charge flowing through a particular area in unit time. In other words, it is the rate of flow of electric charges.
- Conventionally, in an electric circuit, the direction of electric current is taken as opposite to the direction of the flow of electrons, which are negative charges.
- A continuous and closed path of an electric current is called an electric circuit.

If, Charge = Q, time = t, current = I, then

- I =
^{Q}/_{t}

**SI unit of Electric Charge:** coulomb (C)

- 1 C ≈ 6 x 10
^{18}electrons - 1 electron = 1.6 x 10
^{-19}C charge

**SI unit of Electric Current**: ampere (A)

- One ampere is constituted by the flow of one coulomb of charge per second.
- Smaller quantities of current are expressed in milliamperes (mA) or in microamperes (μA)
- 1mA = 10
^{-3}A - 1μA = 10
^{-6}A

- 1mA = 10

**Ammeter: **

- An instrument called an ammeter measures electric current in a circuit.
- It is always connected in
*series*in a circuit through which the current is to be measured.

**Schematic Diagram of an** **Electric Circuit:**

Note that the electric current flows in the circuit from the positive terminal of the cell to the negative terminal of the cell through the bulb and ammeter.

**Electric Potential and Potential Difference**

The work done to move a unit charge from one point to the other is called the potential difference between two points.

- V =
^{W}/_{Q}

**SI unit of Electric Potential Difference:** volt (V)

One volt is the potential difference between two points in a current carrying conductor when 1 joule of work is done to move a charge of 1 coulomb from one point to the other.

**Voltmeter:**

- The potential difference is measured by means of an instrument called the voltmeter.
- The voltmeter is always connected in
*parallel*across the points between which the potential difference is to be measured.

Voltmeter | Ammeter |

i. It is used to measure the potential difference across two points in an electric circuit. | i. It is used to measure electric current in an electric circuit. |

ii. Its resistance is very high. | ii. Its resistance is very low. |

iii. It is connected in parallel in an electric circuit. | iii. It is connected in series in an electric circuit. |

**Circuit Diagram**

**Ohm's Law**

Ohm’s Law: Potential difference across the two points of a metallic conductor is directly proportional to the current passing through the circuit provided that temperature remains constant.

Mathematical expression of Ohm’s Law:

V ∝ I

⇒ V = IR

R is a constant called resistance for a given metal.

V-I graph for Ohm’s Law:

**Resistance:** It is the property of a conductor to resist the flow of charges through it.

Its SI unit is ohm (Ω).

1 ohm: 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.

Good Conductor | A component of a given size that offers a low resistance is a good conductor. |

Resistor | A conductor having some appreciable resistance is called a resistor. |

Poor Conductor | A component of identical size that offers a higher resistance is a poor conductor. |

Insulator | An insulator of the same size offers even higher resistance. |

**Factors on which the Resistance of a Conductor Depends**

Resistance of a uniform metallic conductor is:

- Directly proportional to the length of the conductor (l).
- Inversely proportional to the area of cross-section (A).
- Directly proportional to the temperature.
- Depend on the nature of the material (ρ).

R = ^{ρl}/_{A}

**Resistivity:**

- ρ (rho) is called the electrical resistivity of the material.
- Its SI unit is Ω m.
- It is a characteristic property of the material.
- The metals and alloys have very low resistivity in the range of 10
^{–8}Ω m to 10^{–6}Ω m. They are good conductors of electricity. - Insulators like rubber and glass have resistivity of the order of 10
^{12}to 10^{17}Ω m. - Both the resistance and resistivity of a material vary with temperature.
- The resistivity of an alloy is generally higher than that of its constituent metals.
- Alloys do not oxidise (burn) readily at high temperatures. For this reason, they are commonly used in electrical heating devices, like electric iron, toasters etc.
- Tungsten is used almost exclusively for filaments of electric bulbs.
- Copper and aluminium are generally used for electrical transmission lines.

**Resistance of a System of Resistors**

**1. Resistors in Series**

- In a series combination of resistors the current is the same in every part of the circuit or the same current through each resistor.
- The total potential difference across a combination of resistors in series is equal to the sum of potential difference across the individual resistors.
- V = V
_{1}+ V_{2}+ V_{3} - Equivalent resistance (R
_{s}) of three resistors in series (R_{1}, R_{2}, and R_{3}) = Sum of R_{1}, R_{2}, and R_{3} - R
_{s}= R_{1}+ R_{2}+ R_{3}

**2. Resistors in Parallel**

- The total current I, is equal to the sum of the separate currents through each branch of the combination.
- I = I
_{1}+ I_{2}+ I_{3} - Potential difference is same across each resistor.
- Equivalent resistance of three resistors in parallel (R
_{1}, R_{2}, and R_{3}) = R_{p} - 1/R
_{p}= 1/R_{1}+ 1/R_{2}+ 1/R_{3}

Advantages of parallel combination over series combination:

- If one appliance stops working or goes out of order, then all other appliances keep on working.
- All appliances can be operated at the same voltage as the electric supply.
- Different appliances have different requirements of current. This cannot be satisfied in series as the current remains the same in series.
- The total resistance in a parallel circuit is decreased.
- All devices can be operated independently with separate switches.

**Heating Effect of Electric Current**

W (work done/hear/electrical energy) = QV = VIt = I^{2}Rt = V^{2}t/R

**Joule's law of heating:** The law implies that heat produced in a resistor is

- directly proportional to the square of current for a given resistance,
- directly proportional to resistance for a given current,
- directly proportional to the time for which the current flows through the resistor.

**Practical Applications of Heating Effect of Electric Current**

The electric laundry iron, electric toaster, electric oven, electric kettle and electric heater are some of the familiar devices based on Joule’s heating.

Electric Bulb:

- The electric heating is also used to produce light, as in an electric bulb.
- A strong metal with high melting point such as tungsten (melting point 3380°C) is used for making bulb filaments.
- The bulbs are usually filled with chemically inactive nitrogen and argon gases to prolong the life of filament.

Fuse:

- It protects circuits and appliances by stopping the flow of any unduly high electric current.
- The fuse is placed in series with the device.
- If a current larger than the specified value flows through the circuit, the temperature of the fuse wire increases. This melts the fuse wire and breaks the circuit.
- For an electric iron that consumes 1 kW electric power when operated at 220 V, a current of (
^{1000}/_{220}) A, that is, 4.54 A will flow in the circuit. In this case, a 5 A fuse must be used.

**Electric Power**

- The rate at which electric energy is dissipated or consumed in an electric circuit is called electric power.
- P = VI = I
^{2}R (use this formula in series connection) = V^{2}/R (use this formula in parallel connection) - The SI unit of electric power is watt (W).
- 1 W is the power consumed by a device that carries 1 A of current when operated at a potential difference of 1 V.
- The commercial unit of electric energy is kilowatt hour (kW h), commonly known as ‘unit’.
- 1kWh = 1000 Wh = 1000 x 60 x 60 Ws = 3600000 ws = 3.6 x 10
^{6}joule

Must Also Prepare this: Electricity Class 10 Important Questions and Answers |

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AmitThe notes were really very helpful! Thank you so much!

BotThx^^

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