Advertisements
Advertisements
प्रश्न
Why does tungsten metal used to make solenoid type coil in an electric bulb?
Advertisements
उत्तर
Tungsten metal is used to make solenoid type coil in an electric bulb because:
- Tungsten metal has high resistance and high melting point (nearly 3422°C)
- Because of current it gets heated at high temperature and emits light.
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?
How does the resistance of a wire vary with its area of cross-section?
Write Joule's law of heating.
An electric heater is connected to the 230 V mains supply. A current of 8 A flows through the heater.
- How much charge flows around the circuit each second?
- 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?
What is nichrome? State its one use.
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?
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?
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?
The elements of electrical heating devices are usually made of:
(a) tungsten
(b) bronze
(c) nichrome
(d) argon
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
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.
Which electric heating device in your home do you think have resistors which control the flow of electricity?
Give Scientific reasons.
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.
Identify the figure and give its use.
What is the heating effect of electric current?
What is a short circuit?
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 ______
A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of:
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.
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?
Name two electric devices for each where
- heating effect of current is used and
- magnetic effect of current is used.
Match the following
| 1. | Bulb | a. | Conductor |
| 2. | Electroplating | b. |
Insulator |
| 3. | Pure water | c. | Heating effect of current |
| 4. | Salt solution | d. | Chemical 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.
What is a trip switch?
Find the odd one out.
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.
