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प्रश्न
Identify the figure and give its use.
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उत्तर
- Figure: MCB (Miniature Circuit Breaker)
- Uses: An MCB is a device which functions as a fuse but does not require replacement. MCB falls down to break the circuit when a heavy amount of current flows through it. Once the fault is rectified, the MCB is reset.
संबंधित प्रश्न
Why does the cord of an electric heater not glow while the heating element does?
Name any two effects of electric current.
An electric heater is connected to the 230 V mains supply. A current of 8 A flows through the heater.
(b) How much energy is transferred to the heater each second?
What is meant by the heating effect of current? Give two applications of the heating effect of current.
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
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
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.
Solve the following example.
Two tungsten bulbs of wattage 100 W and 60 W power work on 220 V potential difference. If they are connected in parallel, how much current will flow in the main conductor?
An electric iron of 1100 W is operated for 2 hrs daily. What will be the electrical consumption expenses for that in the month of April? (The electric company charges Rs 5 per unit of energy).
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.
Answer the following question:
what is the heating effect of the electric current? state any four applications of it?
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.
What is the heating effect of electric current?
What is overloading?
How can overloading be avoided?
Explain the application of heating effect of electric current in an electric bulb with a diagram.
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 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 iron draws a current of 4 A when connected to 220 V mains. Its resistance must be:
Which of the following gases are filled in electric bulbs?
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.
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.
An electrochemical cell converts ______ energy into ______ energy.
A trip switch is a ______ safety device.
Explain why fuse wire is always connected in a series arrangement.
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?
An electric kettle of 2 kW is used for 2h. Calculate the energy consumed in
- kilowatt hour and
- joules.
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?
An electric iron of resistance 20 Ω draws a current of 5 A. The heat developed in the iron in 30 seconds is ______.
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?
