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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.

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प्रश्न

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.

एक पंक्ति में उत्तर
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उत्तर

Resistivity of alloys like nichrome is more than pure metals so they will get heated easily on the passage of a small amount of current. They also have a high melting point and do not oxidize readily at high temperature. So in the electric equipment producing heat e.g. iron, electric heater, boiler, toaster etc, an alloy such as Nichrome is used, not pure metals.

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2018-2019 (March) Set 1

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?


An electric heater is connected to the 230 V mains supply. A current of 8 A flows through the heater. 

(a) How much charge flows around the circuit each second?


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?


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 current passing through an electric kettle has been doubled. The heat produced will become:

(a) half
(b) double
(c) four time
(d) one-fourth 


The elements of electrical heating devices are usually made of:

(a) tungsten
(b) bronze
(c) nichrome
(d) argon


If the current flowing through a fixed resistor is halved, the heat produced in it will become:


Two exactly similar heating resistances are connected (i) in series, and (ii) in parallel, in two different circuits, one by one. If the same current is passed through both the combinations, is more heat obtained per minute when they are connected in series or when they are connected in parallel? Give reason for your answer.


Give a scientific reason.

Tungsten metal is used to make a solenoid type coil in an electric bulb.


Identify the figure and give its use.


Identify the figure and give its use.


Compute the heat generated while transferring 96000 coulombs of charge in two hours through a potential difference of 40 V.


The ‘live’ and the ‘neutral’ wires have potential difference of _______.


The electricity bill specifies the usage in _______.


True or False – If False give the correct answer

The fuse wire does not melts whenever there is overload in the wiring.


Define fuse.


Name some devices that run using heat effect of electric current


Explain the heating effect of electric current.


A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of:


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:


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.


How does use of a fuse wire protect electrical appliances?


What is an electric fuse made up of?


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.


______ wire is used in the filament of the bulbs.


Copper wire offers very little ______ and does not get heated up quickly.


Fuse is a strip of alloy wire which is made up of lead and tin with a very low ______.


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.


Name the effect of the current responsible for the glow of the bulb in an electrical circuit.


What is a trip switch?


The following is not a safety device.


An electrochemical cell converts ______ energy into ______ energy.


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.


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?


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.


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