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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
Compute the heat generated while transferring 96000 coulomb of charge in one hour through a potential difference of 50 V.
An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s.
Name any two effects of electric current.
The safety device based on the heating effect of electric current is called a ______.
What is nichrome? State its one use.
Why are the coils of electric irons and electric toasters made of an alloy rather than a pure metal?
Why is a series arrangement not used for connecting domestic electrical appliances in a circuit?
Write down the formula for the heat produced when a current I is passed through a resistor R for time t.
Derive the expression for the heat produced due to a current 'I' flowing for a time interval 't' through a resistor 'R' having a potential difference 'V' across its ends. With which name is this relation known?
The heat produced by passing an electric current through a fixed resistor is proportional to the square of:
(a) magnitude of resistance of the resistor
(b) temperature of the resistor
(c) magnitude of current
(d) time for which current is passed
If the current flowing through a fixed resistor is halved, the heat produced in it will become:
Give a scientific reason:
For electric power transmission, copper or aluminium wire is used.
Name any six domestic appliances based on the heating effect of electric current.
Write the mathematical expression for Joule’s law of heating.
Which of the following substance contracts on heating?
What is a short circuit?
When does overloading occur?
How can overloading be avoided?
Name some devices that run using heat effect of electric current
Name any two appliances which work under the principle of heating effect of current.
Which of the following is correct?
An electric iron consumes energy at the rate of 420 W when heating is at the maximum rate and 180 W when heating is at the minimum rate. The applied voltage is 220 V. What is the current in each case?
An electric iron draws a current of 4 A when connected to 220 V mains. Its resistance must be:
A current of 1 A is drawn by a filament of an electric bulb. Number of electrons passing through a cross-section of the filament in 16 seconds would be roughly:
The heating element of an electric iron is made up of:
An electric kettle consumes 1 kW of electric power when operated at 220 V. A fuse wire of what rating must be used for it?
Paheli took a wire of length 10 cm. Boojho took a wire of 5 cm of the same material and thickness. Both of them connected the wires as shown in the circuit given in the following figure. The current flowing in both the circuits is the same.
- Will the heat produced in both cases be equal? Explain.
- Will the heat produced be the same if the wires taken by them are of equal lengths but of different thickness? Explain.
What are the uses of electromagnets?
It would cost a man Rs. 3.50 to buy 1.0 kW h of electrical energy from the Main Electricity Board. His generator has a maximum power of 2.0 kW. The generator produces energy at this maximum power for 3 hours. Calculate how much it would cost to buy the same amount of energy from the Main Electricity Board.
Copper wire offers very little ______ and does not get heated up quickly.
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 fuse is used in an electric circuit to stop high currents flowing through the circuit.
The electric fuse works on the Joule heating principle.
1 kWh is equal to ______.
In which of the following applications of Iron, rusting will occur most? Support your answer with valid reason.
| A | B | C | D |
 |
 |
 |
 |
In a set up the students coated iron nails with zinc metal and noted that, iron nails coated with zinc prevents rusting. They also observed that zinc initially acts as a physical barrier, but an extra advantage of using zinc is that it continues to prevent rusting even if the layer of zinc is damaged. Name this process of rust prevention and give any two other methods to prevent rusting.
State the law that explains the heating effect of current with respect to the measurable properties in an electrical circuit.
An electric iron is rated 220 V, 2 kW. If the iron is used for 3h daily find the cost of running it for one week if it costs ₹ 4.25 per kWh.
