Advertisements
Advertisements
प्रश्न
Give a scientific reason.
Tungsten metal is used to make a solenoid type coil in an electric bulb.
Advertisements
उत्तर १
- The electric bulb operates under the principle of the heating effect of electric current.
- The bulb’s solenoid-type coil has a very high melting point and high resistance.
- The solenoid-type coil of the lightbulb becomes heated to a high temperature (up to 3400°C) and begins to shine when current is delivered through it.
As a result, tungsten metal creates a solenoid-type coil in an electric bulb.
उत्तर २
- The temperature of a bulb’s filament determines how much light it emits. It rises as the temperature does.
- The material used to construct a lightbulb's filament should have a very high melting point so that it can be heated to a high temperature by running a current through it without melting. We are able to get more light as a result. Tungsten has an extremely high melting point. It is possible to heat tungsten wire to around 3400°C.
Hence, tungsten is used to make a solenoid type coil (filament) in an electric bulb.
APPEARS IN
संबंधित प्रश्न
An electric heater of resistance 8 Ω draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.
Name any two effects of electric current.
The safety device based on the heating effect of electric current is called a ______.
Write Joule's law of heating.
How does the resistance of a wire vary with its:
diameter?
An electric kettle rated at 220 V, 2.2 kW, works for 3 hours. Find the energy consumed and the current drawn.
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 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.
An electric fuse works on the:
(a) chemical effect of current
(b) magnetic effect of current
(c) lighting effect of current
(d) heating effect of current
The elements of electrical heating devices are usually made of:
(a) tungsten
(b) bronze
(c) nichrome
(d) argon
The electrical resistivities of four materials P, Q, R and S are given below:
| P | `6.84xx10^8`Ωm |
| Q | `1.70xx10^8`Ωm |
| R | ` 1.0xx10^15`Ωm |
| s | `11.0xx10^-7`Ωm |
Which material will you use for making: (a) heating element of electric iron (b) connecting wires of electric iron (c) covering of connecting wires? Give reason for your choice in each case.
Which electric heating device in your home do you think have resistors which control the flow of electricity?
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.
Name the factors on which the heat produced in a wire depends when current is passed in it, and state how does it depend on the factors stated by you.
The ‘live’ and the ‘neutral’ wires have potential difference of _______.
These days when current in the circuit suddenly increases _______ switches are used.
A coil of an alloy _______ is used in electric heater cooker as a resistor.
Which of the following substance contracts on heating?
Right or wrong sentence.
Live wire and neutral wires have a 220 V potential difference.
Explain the application of heating effect of electric current in an electric bulb with a diagram.
Heating effect of current is called ______
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 kettle consumes 1 kW of electric power when operated at 220 V. A fuse wire of what rating must be used for it?
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).
When a switch is in OFF position,
- circuit starting from the positive terminal of the cell stops at the switch.
- circuit is open.
- no current flows through it.
- current flows after some time.
Choose the combination of correct answer from the following.
An MCB can be used instead of a fuse in an electrical circuit.
What are the uses of electromagnets?
______ wire is used in the filament of the bulbs.
The following is not a safety device.
An electric fuse is a wire made up of a material having ______ melting point.
A fuse is used in an electric circuit to stop high currents flowing through the circuit.
If 220 V potential difference is applied across an electric bulb, a current of 0.45 A flows in the bulb. What must be the power of the bulb?
1 kWh is equal to ______.
