Advertisements
Advertisements
प्रश्न
In an electric radiator or room heater, state with reason, why the porcelain tube wound with a nichrome wire is placed between the pole and principal focus of the parabolic concave reflector.
Advertisements
उत्तर
In this position, when current passes through the nichrome wire, it becomes red hot and the concave reflector helps in spreading the heat radiation in the room because it forms a divergent beam on account of the heating element being placed between the pole and the principal focus of the reflector.
संबंधित प्रश्न
Name the commercial unit of electric energy.
A bulb marked 12 V, 24 W operated on a 12 volt battery for 20 minutes. Calculate:
(i) the current flowing through it, and
(ii) the energy consumed
An electric toaster draws 8 A current in a 220 V circuit. It is used for 2 h. Find the cost of
operating the toaster if the cost of electrical energy is Rs. 4.50 per kWh.
An electric kettle is rated 2.5 kW, 250 V. Find the cost of running the kettle for two hours at Rs. 5.40 per unit.
The diagram above shows a circuit with the key k open. Calculate :
(i) the resistance of the circuit when the key k is open.
(ii) the current drawn from the cell when the key k is open.
(iii) the resistance of the circuit when the key k is closed.
(iv) the current drawn from the cell when the key k is closed.
Write the SI units for:
(a) Electric current
(b) Potential difference
(c) Charge.
An electric current is passed through a metallic wire. The wire gets heated up. Give the reason. Is it possible to melt the wire by passing a heavy current?
Which material is the calorimeter commonly made of? Give one reason for using this material.
Establish the relation that heat produced in a metallic conductor due to the flow of current is V2t/R joules, where V is the potential difference across the ends of the conductor, R its resistance and t is the time in second for which current flows.
Two resistances R1 = 4Ω and R2 = 6Ω are connected in series. The combination is connected with a battery of e.m.f. 6V and negligible resistance. Calculate:
(i) the heat produced per minute in each resistor,
(ii) the power supplied by the battery.
