Advertisements
Advertisements
Question
What is meant by "electric power"?
Advertisements
Solution
The energy required per unit of time is called electrical power.
RELATED QUESTIONS
The table below shows the current in three different electrical appliances when connected to the 240 V mains supply:
| Appliance | Current |
| Kettle | 8.5 A |
| Lamp | 0.4 A |
| toaster | 4.8 A |
- Which appliance has the greatest electrical resistance? How does the data show this?
- The lamp is connected to the main supply by using a thin, twin-cored cable consisting of live and natural wires. State two reasons why this cable should not be used for connecting the kettle to the mains supply.
- Calculate the power rating of the kettle when it is operated from the 240 V mains supply.
- A main takes the kettle abroad where the mains supply is 120 V. What is the current is the kettle when it is operated from the 120 V supply?
Two resistors A and B of resistance 4 Ω and 6 Ω respectively are connected in parallel. The combination is connected across a 6 volt battery of negligible resistance. Calculate: (i) the power supplied by the battery, (ii) the power dissipated in each resistor.
An immersion heater rated 1000 W, 220 V is used to heat 0.01 m3 of water. Assuming that the power is supplied at 220 V and 60% of the power supplied is used to heat the water, how long will it take to increase the temperature of the water from 15°C to 40°C?
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.
Define 1 kilowatt hour.
A simple electric circuit has 24 V battery and a resistor of 60 Ω. What will be the current in the circuit? The resistance of the connecting wires is negligible.
A simple electric circuit has a 30 V battery and a resistor ot 60 o. What will be the current in the circuit? The resistance of the oonnecting wires is negligible.
The electric bulbs used these days have a coil-coiled filament. State its reason.
An electric filament lamp is connected to a supply of voltage higher than the recommended value. Give reasons, why compared with a normal performance, the lamp emits a brighter light and its life is shortened.
Of the three connecting wires in a household circuit: Which two of the three wires are at the same potential? In which of the three wires should the switch be connected?
An electric heater is rated 220 V, 550 W. What does this statement mean?
An electric heater is rated 220 V, 550 W. Electrical energy is also measured in kWh. What do you understand by a kilo-watt-hour?
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?
Out of the three fuses with current ratings 5A, 10A, 15A, which one is to be connected in a geyser circuit marked 3 kW, 220V? Give reason for your answer.
Unit of electric power may also be expressed as:
1 kWh = ____________
What is the meaning of electric power of an electrical device? Write its SI unit.
An overhead tank of capacity 10 k litre is kept at the top of building 15 m high. Water falls in tank with speed 5`sqrt2` m/s. Water level is at a depth 5 m below ground. The tank is to be filled in `1/2` hr. If efficiency of pump is 67.5% electric power used is ______ W.
