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Heating effect of electric current occurs when electric current flowing through any conducting material produces some amount of heat. Heating effect of electric current is used commonly in our day-to-day life. Some instances of heating effect of electric current are electric iron, toaster, kettle, heater, and many more. When an electric current is passed via a conductor, it starts producing heat due to the hindrance caused by the conductor to the current flowing.
Read Also: Magnetic Effects of Electric Current Formula
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Key Terms: Heating Effect, Electric Current, Resistance, Conducting Material, Ohm’s Law, Electric Circuit, Heat
What is Heating Effect of Electric Current?
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While flowing through any conducting material, an electric current produces some amount of heat. This is because resistance properties are present in any type of conducting material. Therefore, when the electric current flows through such materials, resistance opposes the flow of current. The electric currents need to do some work to overcome the resistance and keep flowing through the conducting material.
This work done of the electric current is dissipated in the form of heat.
Frequently Asked Questions about Heating Effect of Electric CurrentQues. What are the factors that affect Heating effect of Electric Current? (3 marks) Ans. The factors that affect the heating effect of electric current include:
Ques. What is Joule’s Equation for electrical heating? (2 marks) Ans. Joule's equation for electrical heating claims that the heating effect generated by an electric current is I, via a conductor of resistance R, for time t can be represented by H = I2Rt. |
Joule’s Law of Heating
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Joule’s law states that the heat produced by electric current while flowing through a conducting material is equal to the product of the square of the current flowing through the conducting material, resistance of that conducting material, and the duration of the flow of current.
If the value of current flowing through a conducting material is ‘i’, the resistance of that material is ‘R’, and the duration of the flow of current through that conducting material is ‘t’, then the heat generated in that material can be represented as ‘H’. Therefore, H = i2Rt.
This can be Derived as Follows
The work done by the electric current is 'W'. It helps the current to overcome the resistance. It can be expressed as W = V.i.t. Here, V = the potential applied across the conducting material, i = current flowing through a conducting material, and t = the duration of the flow of current through that conducting material.
If all the external effects are absent, then the work done by the electric current will be converted into the form of Heat Dissipation.
Therefore, H = V \(\times\) I \(\times\) t
⇒ H = I \(\times\) I \(\times\) R \(\times\) t
Thus, H = i2Rt [putting V = I\(\times\)R, according to Ohm’s Law]
Conclusion Derived from Joule’s Law of heatingBelow observations can be concluded from the above-explained law:
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Applications of Heating Effect of Electric Current
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We use some common appliances and instruments where the heating effect property of the electric current is visible. Here are some of those appliances with their detailed application described as follows.
Electric Bulb or Incandescent Lamp
An electric bulb or a simple incandescent lamp is an easy example to explain the heating effect of electric current. It contains a wire called filament inside it. Tungsten is a common material to build this filament. When the bulb is in a circuit, the current will flow through the filament of the bulb.
The filament will be heated and emit light. A small percentage of the electric current helps to glow light. The rest of the electric current will be wasted in the form of heat dissipation. There are some other examples of the heating effect of the electric current. Discharge lamps and the production of electric arcs are examples of the heating effects of electric current.
Electric Fuse
An electric fuse is a simple circuit interrupting device. It contains a fusible metal wire through which electric current flows. A fuse is used to connect two points of an electric circuit. The material used in the fuse can allow currents to flow through it up to a certain limit.
When the current flowing through the fuse is higher than its rating, then the fuse melts down easily due to the production of heat and light. The current flowing through the fuse will be interrupted. Usually, the fusing element has a lower melting point. It will prevent any type of accident if the current exceeds the safe value.
Electric Heater, Electric Iron, Toaster
Electric Heater, Electric Iron, and toasters work similarly. Those appliances have metal wires with high resistance inside. Nichrome(an alloy made of 80% of Nickel and the rest is Chromium) is the most common wire used here as a coil. When the electric current passes through this coil, a significant amount of heat will be generated in the coil. This heat will be used based on the appliances.
Things to Remember
- Electric energy supplied to an electric bulb causes heat in the filament. Which gives it light. The heating of an electric bulb happens because of heating effect of the electric current.
- The electric current produces heat to overcome the resistance. This resistance comes from the conductor through which it passes. Higher resistance generates a higher amount of heat.
- Joule’s Law of Heating: According to this law, the heat produced in a resistor is directly proportional to the square of current applied to it, directly proportional to the resistance for a given current, and directly proportional to the duration the current is flowing through it.
- Electric Bulb: The filament of an electric bulb produces light due to the heating effect of electricity. The filament of a light bulb is usually constructed of tungsten metal, which has a melting temperature of 3380°C.
- Electric Iron: Electric iron is made of alloys with a high melting point. Electric heaters and geysers use the same technology.
- Electric Fuse: Electric fuses are used to protect electrical appliances from high voltage. Aluminium, copper, iron, lead, and other metals or metal alloys are used to make electric fuses. Fuse wire melts in the event of a larger voltage flow than is specified, protecting the electric equipment.
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Sample Questions
Ques. State the difference between the wire used in the element of an electric heater and in a fuse wire. (1 Mark) [CBSE 2013]
Ans. The wire used in the element of electric heater has a high resistivity and has a high melting point, i.e. even at a high-temperature element does not burn while fuse wire has a low melting point and high resistivity.
Ques. Write down the drawbacks of the heating effect of electric current? (2 Marks)
Ans. There are two main drawbacks of the heating effect of electric current. Those are as follows:
- Heating effect of electric current causes loss of energy.
- The heating effect of electric current may cause damage to electric instruments and appliances.
Ques. What is a Nichrome wire? Why is Nichrome wire used in electric heaters? (3 Marks)
Ans. Nichrome is an alloy of Nickel and Chromium. In it, 80% Nickel and 20% Chromium are there.
Nichrome wire is used in electric heaters due to its high melting point. It will not melt due to the production of a significant amount of heat. Apart from that, it has high resistance. The heat generation is directly proportional to the resistance. Therefore, the high value of resistance will cause better heat generation.
Ques. Define the Heating Effect of Electric Current. (3 Marks)
Ans. Whenever an electric current gets passed through the conductor, it produces heat because of the hindrance caused due to the conductor to the current flowing. The total work done for overcoming this hindrance to the electric current produces heat in the conductor. This is referred to as the heating effect of current. This heating effect is dependent on three factors which are as follows.
- The resistance of the conductor.
- Duration of the flow of the current.
- The amount of the current flowing.
Ques. What will be the value of heat production, if the current flowing through a material is doubled? Derive the expression using Joule’s formula for the heating effect of electric current. (3 Marks)
Ans. According to Joule’s law, the heat produced in a conducting material is = H = i2Rt. Here, i = current flowing through a conducting material, and t = the duration of the flow of current through that conducting material.
If the value of current is doubled, then the new value of current will be 2i. Now, production of heat = H = (2i)2Rt = 4i2Rt.
Therefore, the production of heat will be four times more than the previous one.
Ques. The electric heater is rated at 2-kilowatt electrical energy costing 4 rupees per kilowatt-hour. What is the cost of using the heater for 3 hours? (3 Marks)
Ans. The electric heater rating is 2kW
This means,
Power of electric heater (P) = 2 kW
Time for which the cost is to be calculated (t) = 3 hours
Thus, total electrical energy consumed (E),
E = P x t
= 2kW x 3 h
= 6 kWh
Cost of 1 unit = Rs. 4
Thus,
Cost of electricity (electrical energy consumed by electric heater for every 3 hours) = 6kWh x 4 = Rs. 24
Ques. Two identical wires one of nichrome and the other of copper are connected in series and a current (I) is passed through them. State the change observed in the temperatures of the two wires. Justify your answer. State the law which explains the above observation. (3 Marks) [CBSE 2012]
Ans. The resistivity of nichrome is more than that of copper so its resistance is also high. Therefore, a large amount of heat is produced in the nichrome wire for the same current as compared to that of copper wire. Accordingly, more change in temperature is observed in the nichrome wire. This is explained by Joule’s law of heating.
Joule’s law of heating: States that the amount of heat produced in a conductor is
(i) directly proportional to the square of the current flowing through it, i.e. .
(ii) directly proportional to the resistance offered by the conductor to the current, i.e. .
(iii) directly proportional to the time for which current is flowing through it, i.e.
Combining these, we get H ∝ I2Rt
Or H = KI2RT
where K is proportionality constant and in the SI system, it is equal to one.
Ques. Define Joules’s Law of heating. (1 mark)
Ans. According to Joule’s law of Heating, the heat produced in a resistor is directly proportional to the square of current applied to it, directly proportional to the resistance for a given current, and directly proportional to the duration the current is flowing through it.
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