In this article we will try to provide all physics electricity formulas for class 10 science chapter 12.

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The movement of charge in a conductor from positive terminal to negative terminal is referred to as electricity. Electricity has a wide range of uses and applications. It serves as a medium for supplying power to electrical devices. We already know that the flow of charge generates current, which we call electricity.

To understand how electricity is produced, we must first understand the various basic parameters associated with it, such as voltage, current, resistance, conductivity, and the relationships between these quantities.

## Symbols and Notations

### Physical quantities, symbols and SI Units

### Symbols for commonly used electrical components

## Formulas of electricity

Given below are all the formulas used for class 10 electricity chapter.

- Charge q on a body is always denoted by

$q = ne$

where n = any integer positive or negative and $e =1.602 \times 10^{-19} C$ i. e., charge on an electron or proton. - $Work\; done = charge \times potential $ or potential difference

Mathematically,

$W=qV=q(V_2V_1)\; Joule$ - $Electric\; Current = \frac{charge}{time}$

Or,

$I=\frac{q}{t}\;Ampere$ -
**Ohm’s Law**

$Resistance=\frac{potential\; difference}{current}$

Or,

$R=\frac{V}{I}$ -
**Resistance in terms of resistivity**

$R=\frac{\rho l}{A}$ -
**Resistance in series combination**

$R_s=R_1+R_2+R_3+…..$ -
**Resistance in parallel combination**

$\frac{1}{R_p}= \frac{1}{R_1}+ \frac{1}{R_2}+ \frac{1}{R_3}+…..$ -
**Electrical Power**

$P=VI=I^2R=\frac{V^2}{R}$ -
**Power in Series**

$\frac{1}{P_s}= \frac{1}{P_1}+ \frac{1}{P_2}+ \frac{1}{P_3}+…..$ -
**Power in parallel**

$P_p=P_1+P_2+P_3+…..$ -
**Electrical Energy**

$E-Vit=I^2Rt=\frac{V^2}{R}t$ -
**Heat produced**

$H-Vit=I^2Rt=\frac{V^2}{R}t$

## Solved Examples

**Question 1 **

When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.

Solution

Here,

Battery Voltage $V= 12 V$

Current in circuit $I=2.5mA=2.5\times 10^{-3}A$

Resistance of the resistor $R=?$ is to be calculated

We know that from Ohm’s Law

$R=\frac{V}{I}$

Putting in the values we get

$R=\frac{12V}{2.5\times 10^{-3}A}$

$=4.8\times 10^{3}VA^{-1}=4.8\times 10^{3}\Omega $

**Question 2**

An electric heater of resistance $8\Omega$ draws 15 A from the service mains for 2 hours. Calculate the rate at which heat is developed in the heater.

Solution

It is given in the question that

Heater resistance $R=8\Omega$

Current drawn, $I=15 A$

Time for which current is drawn

$t=2h=2\times 60\times 60 \;sec=7200\; sec$

Rate of heat developed $P=?$ which is to be calculated

We know that

Rate of heat developed = rate at which power is consumed.

$P=I^2R$

Putting in the value we get,

$P=(15 A)^2\times 8\omega=1800W$

The rate of heat developed is

$P=1800 J/s$ Test Yourself on questions based on these formulas

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