Advertisements
Advertisements
प्रश्न
A metal sphere cools at the rate of 4°C / min. when its temperature is 50°C. Find its rate of cooling at 45°C if the temperature of surroundings is 25°C.
Advertisements
उत्तर
Given that for the metal sphere
`((d theta)/dt)_1=4^@`C/min,
`theta_1=50^@C, theta_2=45^@ and theta_0=25^C`
By Newton's law of cooling,
`((d theta)/dt)=k(theta-theta_0)`
`therefore((d theta)/dt)_1/((d theta)/dt)_2=((theta_1-theta_0))/((theta_2-theta_0)`
`therefore((d theta)/dt)_1/((d theta)/dt)_2=((50^@-25^0))/((45^@-25^@)`
`therefore ((d theta)/dt)_2=20^@/25^@*((d theta)/dt)_1=20^@/25^@*4=3.2`
`therefore ((d theta)/dt)_2=3.2^@`C/min
APPEARS IN
संबंधित प्रश्न
Define emissive power and coefficient of emmision of a body.
The light from the Sun is found to have a maximum intensity near the wavelength of 470 nm. Assuming the surface of the Sun as a black body, the temperature of the Sun is _____________.
[Wien's constant b = 2 .898 x l0- 3mK]
The susceptibility of magnesium at 300 K is 2.4 x 10-5. At what temperature will the susceptibility increase to 3.6 x 10-5?
A body cools from 80° C to 70° C in 5 minutes and to 62° C in the next 5 minutes. Calculate the temperature of the surroundings.
Why do marine animals live deep inside a lake when the surface of the lake freezes?
A spherical shell is heated. The volume changes according to the equation Vθ = V0 (1 + γθ). Does the volume refer to the volume enclosed by the shell or the volume of the material making up the shell?
The temperature of water at the surface of a deep lake is 2°C. The temperature expected at the bottom is
A spinning wheel is brought in contact with an identical wheel spinning at identical speed. The wheels slow down under the action of friction. Which of the following energies of the first wheel decreases?
(a) Kinetic
(b) Total
(c) Mechanical
(d) Internal
A spinning wheel A is brought in contact with another wheel B, initially at rest. Because of the friction at contact, the second wheel also starts spinning. Which of the following energies of the wheel B increases?
(a) Kinetic
(b) Total
(c) Mechanical
(d) Internal
In a calorimeter, the heat given by the hot object is assumed to be equal to the heat taken by the cold object. Does it mean that heat of the two objects taken together remains constant?
A person's skin is more severely burnt when put in contact with 1 g of steam at 100°C than when put in contact with 1 g of water at 100°C. Explain
The atmospheric temperature in the cities on sea-coast change very little. Explain
Should a thermometer bulb have large heat capacity or small heat capacity?
Water equivalent of a body is measured in ___________ .
Two bodies at different temperatures are mixed in a calorimeter. Which of the following quantities remains conserved?
The temperature of a solid object is observed to be constant during a period. In this period
(a) heat may have been supplied to the body
(b) heat may have been extracted from the body
(c) no heat is supplied to the body
(d) no heat is extracted from the body
The volume of a glass vessel is 1000 cc at 20°C. What volume of mercury should be poured into it at this temperature so that the volume of the remaining space does not change with temperature? Coefficients of cubical expansion of mercury and glass are 1.8 × 10–6 °C–1 and 9.0 × 10–6 °C–1 , respectively.
Define one mole.
Explain the meaning of heat and work with suitable examples.
Two tumblers of A and B have water at 50°C temperature. If the water from A and B is poured into tumbler C. The temperature of C is ______.
Temperature in the form of energy.
Give reasons for the following:
Hot metal ball of 80° C is dipped into water of 80°C. The ball will not contract.
The degree of hotness and coldness of a body is called ______.
Heat given to a body that raises its temperature by 1°C is ______.
The temperature of a liquid drops from 365 K to 361 K in 2 min. Find the time during which the temperature of the liquid drops from 344 K to 342 K.
(Take, room temperature = 293 K)
When two bodies at different temperatures are placed in contact, heat flows from ______.
Which of the following correctly differentiates heat from temperature?
