The heating effect of electric current is an important phenomenon that is used in our daily lives. When electric current flows through the resistive element, heat is produced in the element, and this effect is called the heating effect of electric current.
Let us first understand what electric current is to comprehend better how the heating effect happens with the flow of electric current.
What is an Electric Current?
The rate of flow of electric charges( electrons, holes, or ions) through a material is called an electric current. The current’s magnitude depends on the material’s electrical resistance and potential difference across the material.
We can define the electric current with the following mathematical expression.
For example, if the charge is 10 Coulomb and the time is 5 seconds, the current will be 10/5= = 2 ampers.
The current is measured in amperes, and this is the SI unit of current.
Heating effect of Electric Current
The resistive material produces heat when the electric current flows through it. Here, resistive material means the materials that oppose the electric current. The process of heat generation by passing current through the resistive materials is called the heating effect of electric current. The amount of heat energy produced on two important electrical quantities- electric current and resistance of the material.
Joule derived a formula describing this heating phenomenon, and the principle is called Joule’s First Law.
Joule’s law states that the amount of heat produced in the material is;
- Proportional to the Square of the current(I2)
- Proportional to the resistance of the material(R)
- Time(t) for electric current flows through the material.
Thus, the mathematical expression of heat produced in the material can be given by;
From the above expression, it is clear that the conductor that has more resistance can produce more heat.
The formulas of the heating effect of electric current are given below.
Let us understand this with a numerical example.
Calculate the heat energy produced in resistance of 10 Ω when 2 Amperes current flows through it for 5 minutes.
The amount of heat produced
Q = I2 R T
= 22 x 10 x 300
Q =12000 J
Some common examples of the heating effect of current are listed below.
- The incandescent lamp produces light when the current flows through its filament.
- Electric iron has a resistive element, and it produces heat when current flows through its element,
- When the current passes through the heater element. It produces heat,
- The immersion heater rod is dipped in the water, and current passes through its heating element. Then, the heat produced in the element heats up the water.
Applications of Heating Effect of Electric Current:
The following are the common applications of electric heating.
- Electric Heating: Devices like electric stoves, water heaters, space heaters, and toasters use this principle of electric heating to produce heat for cooking and other purposes.
- Electric Kettles: Electric kettles utilize the heating effect of current to boil water quickly for applications such as making tea or coffee.
- Incandescent Light Bulbs: When the current flows through the tungsten filament, it produces heat and light energy. These types of bulbs are not energy efficient because about 95 % of the input energy is lost in heat and only utilize 5 % energy to emit light. LED or CFL bulbs are currently used because they are the most energy-efficient.
- Electric Furnaces: Electric furnaces function on the principle of electric heating. Furnaces are used for heating to melt metals, create glass, or carry out heat treatments. It is also possible to precisely control the desired temperature by electronic control circuitry.
- Soldering and Welding: The heating effect of current is used in soldering and welding processes to melt and join metals together. The electrical current heats the metals’ ends up to their melting points, allowing for a strong bond.
- Hair Dryers and Curling Irons: Devices like hair dryers and curling irons utilize the heating effect of current to generate hot air or heat the styling elements.
- Laboratory Equipment: The heating effect of electric current is used In scientific research and laboratories for various equipment such as hotplates, ovens, and incubators for maintaining the specific temperatures for experiments and processes.
- Electric Blankets and Heating Pads: These electric products use electric heating to provide warmth and comfort during cold weather.
- Food Industry: Devices like Electric ovens, grills, and fryers in the food industry utilize electric heating to cook and prepare food items quickly and efficiently.
- Space Exploration: The spacecraft components are heated by electric heating to prevent them from freezing in the extreme cold of outer space.
- Protection of Electric Circuits: Fuses are used to protect the electric and electronic circuits in the event of faults. When the current is more than the rated capacity of the fuse flows through it, a fuse blows out. The heating effect of the electric current causes the blowing of the fuse.
Solved Examples of the Heating Effect of Electric Current
Example 1: An electrical appliance that has 5 ohms resistance produces 150 J of heat energy when current flows through it for 5 seconds. Calculate the potential difference of the appliance.
From Ohm’s law.
Therefore, the potential difference across the heating element is 20 V.
Example 2: An electric toaster has 5 ohms resistance. Calculate the heat produced by it when 3 amperes current flows through it for 10 minutes.
Example 3: The voltage across a heating element is 20 volts when the heating element produces heat energy of 150 J in 10 seconds. Find out the current flowing through the element.