Joule's law of Heating & Joules First Law

Edited By Vishal kumar | Updated on Nov 20, 2024 03:00 PM IST

As the electric current flows through the circuit, it increases the internal power of the conductor, resulting in the collision of electrons with the conductor atoms, which in turn leads to heat production. To measure the amount of heat transfer as a result of this collision, Joule, an English scientist, proposed Joule's law. In this article, we will study Joule’s Law of Heating and solve the numerical for better understanding.

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This Story also Contains

Joule’s Law of Heating
Derivation of Joule's first law
Applications of Joule's Law
Solved Examples of Joule's law

Joule's law of Heating & Joules First Law

Joule’s Law of Heating

Joule's law explains the heat produced in a conductor and the factors affecting it. "The heat generated in the conductor due to the flow of electricity is directly proportional to the square of the current passing through it, the resistance of the conductor, and the time for which the current passes." Joule's law of heating is also termed as Joule's first law.

Joules law is mathematically represented by the following Equation

$$
H=I^2 R t
$$
Where:

$H=$ Heat produced (in joules)
$I=$ Current (in amperes)
$R=$ Resistance of the conductor (in ohms)
$t=$ Time (in seconds)

Joule's law is a mathematical interpretation of a scale in which resistance to a circuit converts electrical energy into thermal energy.

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Derivation of Joule's first law

When a current $I$ flows through a resistor $R$, the work done in time $t$ is given by:

$$
W=V I t
$$

where $V$ is the potential difference.

Using Ohm's law $V=I R$, the work done becomes:

$$
W=(I R) I t=I^2 R t
$$

The work done by the current in the resistor is entirely converted into heat energy (neglecting other losses). Thus:

$$
H=I^2 R t
$$

Explanation of Joule's law

To undertsand the concept of joule's law let's understand the terms associated with it in brief:

1. Current (I): Heat increases with the square of the current. If the current doubles, the heat increases fourfold.
2. Resistance (R): Higher resistance produces more heat for the same current and time.
3. Time (t): Heat is proportional to the duration of the current flow.

Applications of Joule's Law

Electric heaters: Heat is generated in devices like room heaters and electric kettles.
Fuses: Joule's law explains why fuses melt when excessive current flows through it.
Electric Bulb: The filament glows due to the heat generated by electric current.

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Solved Examples of Joule's law

Q1) Calculate the thermal energy produced to withstand 5 Ω when the current 3 flows through it for 2 minutes.

Solution:

The temperature generated by the operator is given in the formula:

$$
H=I^2 R t
$$
$t=$ Time (in seconds) $=2$ minutes $=2 \times 60=120$ seconds

Substitute the values:

$$
\begin{gathered}
H=(3)^2 \times 5 \times 120 \\
H=9 \times 5 \times 120=5400 \text { joules }
\end{gathered}
$$

Q2) The 300 Ω resistance heater is connected to the main feed for 30 minutes. If 10 current flows through a heater then what is the heat generated in the heater?

Solution:

The temperature generated by the heater is calculated as follows:

H = I²RT

- $t=$ time ( 30 minutes $=30 \times 60=1800$ seconds)

Substitute the values

$$
H=(10)^2 \times 300 \times 1800
$$

$$
H=100 \times 300 \times 1800=54,000,000 or 54 \mathrm{~MJ}
$$

Frequently Asked Questions (FAQs)

1. What Is the Joule heating effects of Joules Heating Caused by Electric Current?

When electrical energy passes through the conductor, it increases the internal energy of the system, which in turn increases the energy of the atomic net and its molecules, which in turn leads to heat production. The heat generated in the system mainly depends on the major factors, namely

Electrical resistance provided by the operator is more resistance; there will be more heat to be produced.

The more current it flows, the more time it has, the more heat it produces.

The current value exceeds the driver. The higher the current size; heat is highly generated.

2. What are some other uses of Joules law?

1. Electric Heating Device

Other electrical appliances such as an electric heater, an electric toaster, and an electric heater are based on the current energy efficiency policy. In these applications, Nichrome (nickel alloy and chromium) is used as a heating element in many electrical devices. This is for the following reasons,

Nichrome has some high opposition.

Nichrome has a very melting point.

Nichrome is not easily integrated.

2. Fuse cable

Fuse cord is a mixture that contains 37% lead and 63% tin. Fuse cable is always connected to the series in the electrical circuit. With its high resistance to low melting point, when a large amount of electrical energy flows through the electrical circuit, the fuse wire melts, thus making the circuit open and preventing any damage to electrical equipment.

3. Electric Lamp

The power cord provides very high resistance to electrical flow, which is why a high temperature is produced. This cord, when intensified by incandescence, emits light. The most used cable is Tungsten, which has a high melting point of 3380 ° C.

Electric arc and electric heating are also based on the joule heating effect of current electric heating.

Joules law of electric heating does not help even when the concept is used in systems such as transformers and dynamos. These are devices that help reduce energy loss due to the heat joule heating effect of electrical energy.

Other energy heating applications are:

Water heater

Incandescent lamp (when its cord is heated produces light).

Fuse (fuse melts and stops the flow of comments now in the region, reducing damage to home devices)

Electrical metal

Electric stove.

Thermistors: Thermistors are a type of resistance to their resistance when changes occur.

3. What About Joule vs. Watt?

Joule is a power unit of SI; it represents the amount of energy contained in the body. Watt is a measure of power conversion and is a unit of power SI.

Power = Time Power Time

Here unit Joule is equal to the value of a watt unit per second unit.

Watts = Joules / time

Energy is a measure of energy consumption per system.

1 Joule per second = 1 Watt

4. What is the significance of the Joule Act?

Joules law of temperature states that if the 'i' current passes through the resistor 'r' and the time 't' then the heat generated on the conductor is equal to the product of the square, the resistance at the same time.

5. What can Joules law predict?

Joules law, on electricity, is a mathematical definition of the rate at which circuit resistance converts electrical energy into thermal energy. ... You have found that the heat from a second equals the amount of electricity absorbed, or the loss of energy.

6. What is Joules law for burning section 10?

Joules law of temperature states that if the 'i' current passes through the resistor 'r' and time 't' then the heat generated in the conductor is equal to the product of the square square, the time resistance. H = i 2 rt.

7. Who got the Joule?

James Prescott Joule

James Prescott Joule, (born December 24, 1818, at Salford, Lancashire [now Greater Manchester], England - died October 11, 1889, Sale, Cheshire), an English scientist who discovered that different forces - mechanical, electrical, and thermal - alike is the same and can be changed to something else.