Advertisements
Advertisements
प्रश्न
When a current of 4.0 A passes through a certain resistor for 10 minutes, 2.88 × 104 J of heat are produced. Calculate
the power of the resistor.
the voltage across the resistor.
Advertisements
उत्तर
I = 4.0 A
H = 2.88 x 104 J
t = 10 minutes = 10 x 60 = 600 s
Power `=H/t=(2.88x10^4)/60=48W`
V`=p/I=48/4=12V`
APPEARS IN
संबंधित प्रश्न
1 kWh = ________ J
At what frequency is AC supplied to residential houses?
If a bulb of 60W is connected across a source of 220V, find the current drawn by it.
What is meant by "electric power"?
Define kilowatt-hour.
How many joules are there in one kilowatt-hour?
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?
Which of the following is the most likely temperature of the filament of an electric light bulb when it is working on the normal 220 V supply line?
(a) 500°C
(b) 1500°C
(c) 2500°C
(d) 4500°C
An electric bulb is rated ‘100 W, 250 V’. What information does this convey?
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 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 .
Two resistors A and B of 4 Ω and 6 Ω, respectively are connected in parallel. The combination is connected across a 6 volt battery of negligible resistance. Calculate the power dissipated in each resistor.
Name three main characteristics of an heating element.
Why does not the heating coil produce any visible light? in an electric stove.
If the rating of an electric bulb is 100W – 230V, Explain its meaning.
State other bigger units of electric power and express them in watt.
A bulb is connected to a battery of e.m.f. 6V and internal resistance 2Ω A steady current of 0.5A flows through the bulb. Calculate the heat energy dissipated in the bulb in 10 minutes.
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?
A student wants to use an electric heater, an electric bulb and an electric fan simultaneously.
How should these gadgets be connected with the mains? Justify your answer giving three reasons.
In the given figure, the emf of the cell is 2.2 V, and if internal resistance is 0.6 Ω. Calculate the power dissipated in the whole circuit.
