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प्रश्न
In an electric bulb, coil of _______ metal is used.
विकल्प
copper
tungsten
aluminium
iron
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उत्तर
In an electric bulb, coil of tungsten metal is used.
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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?
Explain why, the current that makes the heater element very hot, only slightly warms the connecting wires leading to the heater.
A heating coil has a resistance of 200 Ω. At what rate will heat be produced in it when a current of 2.5 A flows through it?
What is meant by the heating effect of current? Give two applications of the heating effect of current.
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.
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.
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.
Give Scientific reason.
In practice, the unit kWh is used for the measurement of electrical energy, rather than joule.
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?
Statement 1 : Electric current ( flow of electrons ) creates heat in the resistor.
Statement 2 : Heat in the resistor is created according to the rule of energy conservation.
Explain Statement 1 with the help of Statement 2.
Why does tungsten metal used to make solenoid type coil in an electric bulb?
Name any six domestic appliances based on the heating effect of electric current.
Write the mathematical expression for Joule’s law of heating.
The electricity bill specifies the usage in _______.
What is the heating effect of electric current?
How can overloading be avoided?
Explain the application of heating effect of electric current in an electric bulb with a diagram.
Name some devices that run using heat effect of electric current
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:
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:
The heating element of an electric iron is made up of:
An electric bulb is connected to a 220 V generator. The current is 0.50 A. What is the power of the bulb?
(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).
Your teacher has shown you the following activity.
Activity: Teacher has wound a long insulated piece of wire around an iron nail in the form of a coil. Free ends of the wire are connected to a cell through a switch as shown in the following figure. The current is switched on and some pins are placed near the ends of the nail.
Write down any three questions that come to your mind about this activity.
An electric fuse has a body made of ceramic and two points for connecting the fuse wire.
Name the effect of the current responsible for the glow of the bulb in an electrical circuit.
Name a few appliances which work on the basis of the heating effect of current.
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.
An electric fuse is a wire made up of a material having ______ melting point.
A trip switch is a ______ safety device.
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?
Tara, after completing her exams, went to her grandmother's house along with her younger brother Rahul. One day, Rahul came home after playing and switched on the fan and air conditioner. At the same time, his grandmother was preparing a milkshake for him using a mixer. Suddenly, they heard a big sound and the electricity of the house got shut down. Tara is called an electrician. He said the main reason for supply to shut down was overloading.
- What is overloading?
- Is overloading and short the same? When does short-circuiting take place?
- How can the effects of overloading be avoided?
In which of the following applications of Iron, rusting will occur most? Support your answer with valid reason.
| A | B | C | D |
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 |
 |
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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.
Anannya responded to the question: Why do electrical appliances with metallic bodies are connected to the mains through a three-pin plug, whereas an electric bulb can be connected with a two-pin plug?
She wrote: Three-pin connections reduce heating of connecting wires.
- Is her answer correct or incorrect? Justify.
- What is the function of a fuse in a domestic circuit?
