Understanding Joule's Law of Heating
Joule's law of heating states that the heat produced ($H$) in a conductor is directly proportional to the product of the square of the current ($I$) flowing through it, the resistance ($R$) of the conductor, and the time ($t$) for which the current flows. The formula is:
$H = I^2 R t$
This principle is used in devices designed to generate heat.
Analyzing Device Operations
- Fuse: A fuse wire is designed to have a low melting point and specific resistance. When current exceeds the limit, the heat generated ($H = I^2 R t$) melts the fuse wire, breaking the circuit. This device relies directly on Joule's law.
- Electric Iron: An electric iron contains a heating element (a resistive wire) that gets very hot when current passes through it. This heat is generated based on the principle $H = I^2 R t$ and is used for ironing clothes.
- Electric Kettle: Similar to an electric iron, an electric kettle uses a heating element. Electrical energy is converted into heat energy via $H = I^2 R t$ to heat the water.
- Electric Plugs and Switches: The primary function of plugs and switches is to connect or disconnect electrical circuits. While resistance in the contacts can cause some heating (following $H = I^2 R t$), this is an undesired effect, not the basis of their operation. Their purpose is conduction and interruption, not heat generation. Excessive heating indicates a fault.
Conclusion on Device Function
Based on the analysis, electric plugs and switches are designed for circuit control, not primarily for generating heat using Joule's law, unlike fuses, electric irons, and electric kettles.
Similar Questions
- Which of the following is NOT a Colour created from a combination of two primary Colours?
- Pushkar Mela is held in Pushkar. Which district does it come under?
- The phenomenon of 'dispersion of light' into its seven constituent colours was discovered by ______ in 1666.
- Who was the first person to obtain a spectrum by passing light through a prism?
- At which temperature is the density of water maximum?
- Which of the following equipment is used to transform chemical energy into electrical energy?
- For humans, the audible waves are those that:
- Which of the following is NOT an example of the heating effect of current?
- Which of the following units is used to measure the intensity of sound?
- What is the science or art of designing and accelerating projectiles so as to achieve a desired performance called?
Important Questions from Physics
What is the colour of the light emitted by the Sun?
Lightning occur in the sky when two clouds:
With reference to street-lighting, how do sodium lamps differ from LED lamps?
1. Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps.
2. As street lights, sodium lamps have a longer life span than LED lamps.
3. The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant colour advantages in street lighting.
Select the correct answer using the code given below.
Which one of the following is a reason why astronomical distances are measured in light-years?
In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following?
1. Area of the hole in the lid
2. Temperature of the flame
3. Weight of the lid
Select the correct answer using the code given below.
