Overview: Electricity | Science Class 10 PDF Download

Electric Current

Electric Current Formula and Unit

• Conventional electric current direction is opposite to the flow of electrons.
• Electric current (I) is defined as I = Q/t, where Q is the charge flowing through a conductor in time t.
• The SI unit of charge is the coulomb, and electric current is measured in units of coulombs per second, known as "ampere" (A).
• Electric current flows from the negative terminal to the positive terminal of a cell in a simple electric circuit.
• A typical electric circuit includes components like a lamp, a switch, and a cell.
• In a torch, the battery (cell) enables the flow of charges, causing the bulb to glow due to the electric current.

• A switch in a circuit creates a conducting link between the cell and the bulb, allowing current to flow.
• If the circuit is interrupted or breaks, the current immediately stops flowing, and the bulb ceases to glow.

Electric Potential and Potential Difference

Electric Potential Difference is the driving force behind the flow of electric charges in a circuit, much like pressure differences drive water flow.

It is the work done to move a unit charge between two points in a circuit.
Mathematically:
V=Q/W

• Unit: Measured in volts (V), where 1 volt = 1 joule/coulomb.

• Function: Created by a battery, it pushes charges through a conductor, generating electric current.

• Measurement: A voltmeter, connected in parallel, measures this potential difference.

Electric Current and Circuit Diagram Elements

The schematic diagram represents the different components of a circuit; this is the circuit diagram. These symbols represent the common electrical components.

Ohm’s Law and Resistance

• Ohm’s law states that the voltage or potential difference between two points is directly proportional to the current or electricity passing through the resistance, and directly proportional to the resistance of the circuit.
• The formula for Ohm’s law is V=IR. This relationship between current, voltage, and relationship was discovered by German scientist Georg Simon Ohm.

Ohm’s Law

Most basic components of electricity are voltage, current, and resistance. Ohm’s law shows a simple relation between these three quantities. Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

Ohm’s Law Formula

Voltage= Current× Resistance
V= I×R
V= voltage, I= current and  R= resistance

SI unit of resistance is ohms and is denoted by Ω
This law is one of the most basic laws of electricity. It helps to calculate the power, efficiency, current, voltage, and resistance of an element of an electrical circuit.

Applications of Ohm’s Law: Ohm’s law helps us in determining either voltage, current or impedance or resistance of a linear electric circuit when the other two quantities are known to us. It also makes power calculation simpler.

Resistance of a System of Resistors

Resistors in Series

A series generally means connected along a line, or in a row, or in an order. In electronics, series resistance means that the resistors are connected one after the other and that there is only one path for current to flow through.

Laws of Series Circuits

• Individual resistance add up to the total circuit resistance
• Current through the circuit is the same at every point.
• Individual voltages throughout the circuit add up to the total voltage.

Resistors in Parallel

There are many different ways to organize a parallel circuit. In the practical world, most of the wiring is done in parallel so that the voltage to any one part of the network is the same as the voltage supplied to any other part of it.

Laws of Parallel Circuits

• The reciprocals of all the individual resistances add up to the reciprocal of the total circuit resistance.
• 1/RT = 1/R1 + 1/R2 + 1/R3 …
• Voltage through the circuit is the same at every point.
• Individual current draws throughout the circuit add up to the total current draw.

Heating Effect of the Electric Current

When a current flows through a conductor, heat energy generates in the conductor. The heating effects of electric current depend on three factors:

• The resistance of the conductor. A higher resistance produces more heat.
• The time for which the current flows. The longer the time the amount of heat production is high.
• Higher the current the amount of heat generation is also large.

Hence the heating effect produced by an electric current, I through a conductor of resistance, R for a time, t is given by H = I²Rt. This equation is the Joule’s equation of electrical heating.

Joule’s law states the amount of heat production in a conductor is :

• Directly proportional to the square of electric current flowing through it.
• Is directly proportional to the resistance of the conductor.
• Directly proportional to the time for which electric current flows through the conductor.

Electric Power

Electric power is the rate at which electrical energy is consumed in a circuit. It can be calculated using the formula:

where:

• $P$P is the power in watts (W),
• V is the potential difference in volts (V),
• $I$I is the current in amperes (A),
• R is the resistance in ohms (Ω).

The SI unit of electric power is the watt (W), where 1 watt is the power consumed when 1 ampere of current flows through a circuit with a potential difference of 1 volt.

For practical purposes, larger units like kilowatt (kW) are used, where: 1 kW = 1000 W.

Electric energy is measured in watt hours (Wh), with the commercial unit being kilowatt hour (kWh), also known as a 'unit' of electricity. One kilowatt hour is equal to:$\mathrm{ 1}kWh=3.6\times 106joules\; (J)1\; \backslash text\{\; kWh\}\; =\; 3.6\; \backslash times\; 10^6\; \backslash text\{\; joules\; (J)\}$1 kWh=3.6×106 joules (J)

This unit represents the energy consumed when 1 kilowatt of power is used for 1 hour.