Advertisements
Advertisements
प्रश्न
A heating element using nichrome connected to a 230 V supply draws an initial current of 3.2 A which settles after a few seconds to a steady value of 2.8 A. What is the steady temperature of the heating element if the room temperature is 27.0°C? The temperature coefficient of resistance of nichrome averaged over the temperature range involved is 1.70 × 10−4 °C−1.
Advertisements
उत्तर
Supply voltage, V = 230 V
Initial current drawn, I1 = 3.2 A
Initial resistance = R1, which is given by the relation,
R1 = `"V"/"I"`
= `230/3.2`
= 71.87 Ω
Steady state value of the current, I2 = 2.8 A
Resistance at the steady state = R2, which is given as
R2 = `230/2.8`
= 82.14 Ω
Temperature co-efficient of nichrome, α = 1.70 × 10−4 °C−1
Initial temperature of nichrome, T1 = 27.0°C
Study state temperature reached by nichrome = T2
T2 can be obtained by the relation for α,
α = `("R"_2 - "R"_1)/("R"_1("T"_2 - "T"_1))`
T2 − 27°C = `(82.14 - 71.87)/(71.87 xx 1.7 xx 10^-4)`
= 840.5
T2 = 840.5 + 27
= 867.5°C
Therefore, the steady temperature of the heating element is 867.5°C.
संबंधित प्रश्न
At room temperature (27.0°C) the resistance of a heating element is 100 Ω. What is the temperature of the element if the resistance is found to be 117 Ω, given that the temperature coefficient of the material of the resistor is 1.70 × 10−4 °C−1.
A silver wire has a resistance of 2.1 Ω at 27.5°C, and a resistance of 2.7 Ω at 100°C. Determine the temperature coefficient of resistivity of silver.
Draw labelled graphs to show how electrical resistance varies with temperature for:
1) a metallic wire.
2) a piece of carbon
Show variation of resistivity of Si with temperature in a graph ?
A non-ideal battery is connected to a resistor. Is work done by the battery equal to the thermal energy developed in the resistor? Will your answer change if the battery is ideal?
As the temperature of a metallic resistor is increased, the product of its resistivity and conductivity ____________ .
Two resistors R and 2R are connected in series in an electric circuit. The thermal energy developed in R and 2R are in the ratio ______________ .
When a current passes through a resistor, its temperature increases. Is it an adiabatic process?
As temperature increases, the viscosity of liquids decreases considerably. Will this decrease the resistance of an electrolyte as the temperature increases?
The constants a and b for the pair silver-lead are 2.50 μV°C−1 and 0.012μV°C−2, respectively. For a silver-lead thermocouple with colder junction at 0°C, ______________ .
(a) there will be no neutral temperature
(b) there will be no inversion temperature
(c) there will not be any thermo-emf even if the junctions are kept at different temperatures
(d) there will be no current in the thermocouple even if the junctions are kept at different temperatures
An electric kettle used to prepare tea, takes 2 minutes to boil 4 cups of water (1 cup contains 200 cc of water) if the room temperature is 25°C. (a) If the cost of power consumption is Re 1.00 per unit (1 unit = 1000 watt-hour), calculate the cost of boiling 4 cups of water. (b) What will be the corresponding cost if the room temperature drops to 5°C?
The figure shows an electrolyte of AgCl through which a current is passed. It is observed that 2.68 g of silver is deposited in 10 minutes on the cathode. Find the heat developed in the 20 Ω resistor during this period. Atomic weight of silver is 107.9 g/mol−1.
The higher and lower fixed points on a thermometer are separated by 160 mm. When the length of the mercury thread above the lower point is 40 mm, the temperature reading would be :
Water at 10°C enters into a geyser. The water drawn out from the geyser has a temperature of 60°C and the rate of outflow of water is 18 kg/hr. The rating of the geyser is :
