Advertisements
Advertisements
प्रश्न
Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
उत्तर
The conductors of electric heating devices such as bread toasters and electric irons are made of alloy instead of pure metal for the following reasons:
- The resistivity of an alloy is higher than that of metal, which produces a large amount of heat.
- Oxidation of alloys does not occur quickly at high temperatures.
- There is negligible change in their resistance with increase in temperature.
APPEARS IN
संबंधित प्रश्न
State four most common electrical appliances based on heating effect of electric current. Why do we use finely heated platinum wire in surgery?
Why does the cord of an electric heater not glow while the heating element does?
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?
An electric room heater draws a current of 2.4 A from the 120 V supply line. What current will this room heater draw when connected to 240 V supply line?
Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.
Why does the connecting cord of an electric heater not glow hot while the heating element does?
How much heat will an instrument of 12 W produce in one minute if it is connected to the heat produced by it?
Which of the following characteristic is not suitable for a fuse wire?
(a) thin and short
(b) thick and short
(c) low melting point
(d) higher resistance than rest of wiring
Answer the following question.
Write the mathematical expression for Joule's law of heating.
Name some devices that run using heat effect of electric current
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 bulb is connected to a 220 V generator. The current is 0.50 A. What is the power of the bulb?
Assertion: Bending of wire decreases the resistance of the electric wire.
Reason: The resistance of a conductor depends on length, thickness, nature of material and temperature of the conductor.
Why is parallel arrangement used in domestic wiring?
What is Joule’s heating effect? How can it be demonstrated experimentally? List its four applications in daily life.
Name two electric devices for each where
(i) the heating effect of current is used and
(ii) the magnetic effect of current is used.
What is an electric fuse made up of?
Assertion: A current-carrying wire should be charged.
Reason: The current in a wire is due to the flow of free electrons in a definite direction.
Write an expression for the amount of heat produced in a resistor when an electric current is passed through it stating the meanings of the symbols used.
When a current I flows through a wire of resistance R for time t then the electrical energy produced is given by ______.
