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प्रश्न
In the electric equipment producing heat like iron, electric heater, boiler, toaster etc., an alloy such as nichrome is used, not pure metals.
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उत्तर
The performance and life of a heating element are determined by the material used to make the heating element. The heating element material must have a high melting point, high tensile strength, high resistivity, and a low-temperature coefficient of resistance. Because an alloy's resistivity is greater than that of pure metal, alloys are employed in electrical heating devices rather than pure metals. Furthermore, even at greater temperatures, the alloy does not easily burn (or oxidise).
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संबंधित प्रश्न
The safety device based on the heating effect of electric current is called a ______.
Write Joule's law of heating.
An electric heater is connected to the 230 V mains supply. A current of 8 A flows through the heater.
(b) How much energy is transferred to the heater each second?
Why is a series arrangement not used for connecting domestic electrical appliances in a circuit?
An electric kettle rated at 220 V, 2.2 kW, works for 3 hours. Find the energy consumed and the current drawn.
Why does the connecting cord of an electric heater not glow hot while the heating element does?
Write down the formula for the heat produced when a current I is passed through a resistor R for time t.
An electric iron of resistance 20 ohms draws a current of 5 amperes. Calculate the heat produced in 30 seconds.
The current passing through an electric kettle has been doubled. The heat produced will become:
(a) half
(b) double
(c) four time
(d) one-fourth
If the current flowing through a fixed resistor is halved, the heat produced in it will become:
The electrical resistivities of four materials P, Q, R and S are given below:
| P | `6.84xx10^8`Ωm |
| Q | `1.70xx10^8`Ωm |
| R | ` 1.0xx10^15`Ωm |
| s | `11.0xx10^-7`Ωm |
Which material will you use for making: (a) heating element of electric iron (b) connecting wires of electric iron (c) covering of connecting wires? Give reason for your choice in each case.
Give a scientific reason.
Tungsten metal is used to make a solenoid type coil in an electric bulb.
Give scientific reason :
In the electric equipment producing heat e.g. iron, electric heater, boiler, toaster, etc., an alloy such as Nichrome is used, not pure metals.
Rewrite the following statement by selecting the correct option:
1 A = ____________ mA.
The ‘live’ and the ‘neutral’ wires have potential difference of _______.
What is a short circuit?
Explain the application of heating effect of electric current in an electric bulb with a diagram.
Heating effect of current is called ______
An electric iron draws a current of 4 A when connected to 220 V mains. Its resistance must be:
How does use of a fuse wire protect electrical appliances?
Three incandescent bulbs of 100 W each are connected in series in an electric circuit. In another circuit another set of three bulbs of the same wattage are connected in parallel to the same source.
- Will the bulb in the two circuits glow with the same brightness? Justify your answer.
- Now let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.
Can we use the same fuse in a geyser and a television set? Explain.
An MCB can be used instead of a fuse in an electrical circuit.
What are the factors affecting heating effect of electric current?
Explain the working of an electric fuse.
Match the following
| 1. | Bulb | a. | Conductor |
| 2. | Electroplating | b. |
Insulator |
| 3. | Pure water | c. | Heating effect of current |
| 4. | Salt solution | d. | Chemical effect of current |
A student boils water in an electric kettle for 20 minutes. Using the same mains supply he wants to reduce the boiling time of water. To do so should he increase or decrease the length of the heating element? Justify your answer.
The electric fuse works on the Joule heating principle.
Define the following:
Electrolyte
Tara, after completing her exams, went to her grandmother's house along with her younger brother Rahul. One day, Rahul came home after playing and switched on the fan and air conditioner. At the same time, his grandmother was preparing a milkshake for him using a mixer. Suddenly, they heard a big sound and the electricity of the house got shut down. Tara is called an electrician. He said the main reason for supply to shut down was overloading.
- What is overloading?
- Is overloading and short the same? When does short-circuiting take place?
- How can the effects of overloading be avoided?
Find the odd one out.
1 kWh is equal to ______.
State the law that explains the heating effect of current with respect to the measurable properties in an electrical circuit.
When a current I flows through a wire of resistance R for time t then the electrical energy produced is given by ______.
