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प्रश्न
Name three main characteristics of an heating element.
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उत्तर
The three main characteristics of an heating element are:
(i) It should have a high resistance so that a major amount of electric energy is converted into heat energy.
(ii) It should not get oxidised easily up to a temperature of 1000°C.
(iii) It should have a high melting point and a low thermal Expansion so that it does not get loosened on getting heated.
संबंधित प्रश्न
An electric bulb is connected to a 220 V power supply line. If the bulb draws a current of 0.5 A, calculate the power of the bulb.
The table below shows the current in three different electrical appliances when connected to the 240 V mains supply:
| Appliance | Current |
| Kettle | 8.5 A |
| Lamp | 0.4 A |
| toaster | 4.8 A |
- Which appliance has the greatest electrical resistance? How does the data show this?
- The lamp is connected to the main supply by using a thin, twin-cored cable consisting of live and natural wires. State two reasons why this cable should not be used for connecting the kettle to the mains supply.
- Calculate the power rating of the kettle when it is operated from the 240 V mains supply.
- A main takes the kettle abroad where the mains supply is 120 V. What is the current is the kettle when it is operated from the 120 V supply?
1Kwh =`( 1 "volt "xx 1 am pere xx.............)/1000`
The diagram above shows a circuit with the key k open. Calculate :
(i) the resistance of the circuit when the key k is open.
(ii) the current drawn from the cell when the key k is open.
(iii) the resistance of the circuit when the key k is closed.
(iv) the current drawn from the cell when the key k is closed.
A simple electric circuit has 24 V battery and a resistor of 60 Ω. What will be the current in the circuit? The resistance of the connecting wires is negligible.
A coil of copper wire is connected to a galvanometer. What would happen if a bar magnet is:
(i) Pushed into the coil with its north pole entering first?
(ii) Held at rest inside the coil?
(iii) Pulled out again?
If the rating of an electric bulb is 100W – 230V, Explain its meaning.
An electric bulb is rated as 100W – 250V. What information does it convey? Calculate the resistance of its filament while glowing.
1 mV is equal to:
