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प्रश्न
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उत्तर
Electrical power is defined as the rate at which energy is changed or work is done i.e., the work done per second or energy converted per second.
Electrical appliances come with certain number of watts and volts written on them. Power rating of an electrical appliance gives the knowledge of the safe current limit of an appliance and also indicates the voltage above which the appliance should not be used.
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संबंधित प्रश्न
The diagram below shows a magnetic kept just below the conductor AB which is kept in North South direction.
(i) In which direction will the needle deflect when the key is closed ?
(ii) Why is the deflection produced ?
(iii) What will be the change in the deflection if the magnetic needle is taken just above the conductor AB ?
(iv) Name one device which works on this principle.
The diagram 31 shows a 3 terminal plug socket.
(i) What is the purpose of the terminal E?
(ii) To which part of the appliance is the terminal E connected?
(iii) To which wire L or N, is the fuse connected and why?
The diagram shows a coil connected to a center zero galvanometerG . The galvanometer shows a deflect ion to the right when the north pole N of a powerful magnet is moved to the right as shown .
(i) Explain, why the defelct ion occurs in the galvanometer.
(ii ) State whether th e current in the coil is cl ockwise or anticl ockwise
when viewed from the end P.
(iii ) State th e observation in G when the coil is moved away from north
pole N of the magnet keeping the magnet stationary.
(iv)State the observation in G when both the coil and the magnet are
moved to right at th e same speed .
State three factors on which the heat produced in a metallic wire due to passage of current in it depends.
Why is a concave reflector placed behind the heating element in a room heater.
Three 250 W heaters are connected in parallel to a 100 V supply, Calculate the resistance of each heater.
A family uses a light bulb of 100W, a fan of 100W, and a heater of 1000W, each for 8 hours a day. If the cost of electricity is Rs. 2 per unit, what is the expenditure to the family per day, on electricity?
An electric lamp A of 40 W and another electric lamp B of 100 W are connected to 220 V supply. Calculate the ratio of their filament resistances?
A bulb is marked 100W, 220V and an electric heater is marked 2000 W, 220 V.
(i) What is the ratio between the resistances of these two devices?
(ii) How does the power-voltage rating of a device help us to decide about the type of leads (connecting wires) to be used for it?
(iii) In which of the above two devices, a thicker connecting wire of lead is required?
Unit of electric power may also be expressed as:
