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प्रश्न
What do you mean by power rating of an electrical appliance? How do you use it to calculate
(a) the resistance of the appliance and
(b) the safe limit of the current in it, while in use?
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उत्तर
An electrical appliance such as electric bulb, geyser etc. is rated with power (P) and voltage (V) which is known as its power rating. For example: If an electric bulb is rated as 50W-220V, it means that when the bulb is lighted on a 220 V supply, it consumes 50 W electrical power.
(a) To calculate the resistance of the appliance, the expression is:
Resisteance , R = `"V"^2/"P"`
(b) The safe limit of current I is : I = `"P"/"V"`
संबंधित प्रश्न
A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R’, then the ratio `"R"/"R'"` is ______.
How does the resistance of a wire change when:
its length is tripled?
What possible values of resultant resistance one can get by combining two resistances, one of value 2 ohm and the other 6 ohm?
If two resistors of 25 Ω and 15 Ω are joined together in series and then placed in parallel with a 40 Ω resistor, the effective resistance of the combination is :
(a) 0.1 Ω
(b) 10 Ω
(c) 20 Ω
(d)40 Ω
A graph is plotted taking p.d. along y-axis and electric current along x-axis. Name the physical quantity that represents the slope of this graph (Fig.).
Answer the following question.
While studying the dependence of potential difference ( V) across a resistor on the current (I) passing through it, in order to determine the resistance of the resistor, a student took 5 readings for different values of current and plotted a graph between V and t. He got a straight line graph passing through the origin. What does the straight-line signify? Write the method of determining the resistance of the resister using this graph.
How does the resistivity of an alloy such as constantace depends on temperature.
State expression for Resistance connected in series.
Two wires of the same length and area made of two materials of resistivity ρ1 and ρ2 are connected in series to a source of potential V. The equivalent resistivity for the same area is:
If R1 and R2 be the resistance of the filament of 40 W and 60 W respectively operating 220 V, then:
