Advertisements
Advertisements
प्रश्न
A coil of an alloy _______ is used in electric heater cooker as a resistor.
विकल्प
Stainless steel
Nichrome
Copper
Bronze
Advertisements
उत्तर
A coil of an alloy nichrome is used in electric heater cooker as a resistor.
APPEARS IN
संबंधित प्रश्न
Why does the cord of an electric heater not glow while the heating element does?
An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s.
Give two reasons why nichrome alloy is used for making the heating elements of electrical appliances.
Why are the coils of electric irons and electric toasters made of an alloy rather than a pure metal?
The current passing through a room heater has been halved. What will happen to the heat produced by it?
What is meant by the heating effect of current? Give two applications of the heating effect of current.
Name the material which is used for making the filaments of an electric bulb.
The heat produced in a wire of resistance 'x' when a current 'y' flows through it in time 'z' is given by:
(a) x2 × y × z
(b) x × z × y2
(c) y × z2 × x
(d) y × z × x
Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. Calculate:
- the total current taken from the supply
- the resistance of each heater and
- the energy supplied in kWh to the three heaters in 5 hours.
Heat energy is being produced in a resistance in a circuit at the rate of 100 W. The current of 3 A is flowing in the circuit. What must be the value of the resistance?
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.
Answer the following question:
what is the heating effect of the electric current? state any four applications of it?
Which of the following substance contracts on heating?
Find the odd one out and give its explanation.
When does overloading occur?
What does overloading cause?
How can overloading be avoided?
Explain the heating effect of electric current.
Mark the correct choice
- Assertion: Electric appliances with a metallic body have three wire connections.
- Reason: Three-pin connections reduce the heating of the connecting wires.
An electric iron draws a current of 4 A when connected to 220 V mains. Its resistance must be:
A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of:
Why is parallel arrangement used in domestic wiring?
B1, B2 and B3 are three identical bulbs connected as shown in Figure. When all the three bulbs glow, a current of 3A is recorded by the ammeter A.
- What happens to the glow of the other two bulbs when the bulb B1 gets fused?
- What happens to the reading of A1, A2, A3 and A when the bulb B2 gets fused?
- How much power is dissipated in the circuit when all the three bulbs glow together?
What is Joule’s heating effect? How can it be demonstrated experimentally? List its four applications in daily life.
(a) Observe the diagram given below and state whether the bulb will glow or not when we switch on K.
(b) Is it safe to handle the bulb when the switch is OFF?
(c) Give a reason for your answer in (b).
Unscramble the following words:
SFEU
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.
An electric fuse has a body made of ceramic and two points for connecting the fuse wire.
What are the uses of electromagnets?
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.
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.
What is a trip switch?
The electric fuse works on the Joule heating principle.
In the electric equipment producing heat like iron, electric heater, boiler, toaster etc., an alloy such as nichrome is used, not pure metals.
In which of the following applications of Iron, rusting will occur most? Support your answer with valid reason.
| A | B | C | D |
 |
 |
 |
 |
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?
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.
The graph of voltage vs current for four different materials is shown below.
Which of these four materials would be used for making filament of bulb?
