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3 years ago

Which statement about tempture is correct

Physics

1 answer:

motikmotik3 years ago

7 0

Answer:

B temperature is an indirect measurement of the heat energy in a substance

Explanation:

The concept of temperature can be easily understood by looking at what happens when two objects are placed in contact with each other. By common experience, we know that the hotter object transfers heat energy to the colder object, until the two objects are in thermal equilibrium (= they have same temperature).

Thinking about the example above, we can say therefore that the temperature is an indirect measurement of the heat energy possessed by an object (or substance).

For a monoatomic gas, for instance, we define its internal energy as

$U=\frac{3}{2}nRT$

where n is the number of moles, R is the gas constant, and T is the absolute temperature. From the formula, we see that the temperature is related to the internal energy of the gas, so measuring the temperature means indirectly measuring its internal energy.

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A lamp can work on 50V mains taking 2 amps. What value of resistance must be connected in series with it, so that it can be oper

wolverine [178]

The resistance of the lamp is apparently 50V/2A = 25 ohms.

When the circuit is fed with more than 50V, we want to add
another resistor in series with the 25-ohm lamp so that the
current through the combination will be 2A.

In order for 200V to cause 2A of current, the total resistance
must be 200V/2A = 100 ohms.

The lamp provides 25 ohms, so we want to add another 75 ohms
in series with the lamp. Then the total resistance of the circuit is
(75 + 25) = 100 ohms, and the current is 200V/100 ohms = 2 Amps.

The power delivered by the 200V mains is (200V) x (2A) = 400 watts.

The lamp dissipates ( I² · R ) = (2² · 25 ohms) = 100 watts.

The extra resistor dissipates ( I² · R) = (2² · 75 ohms) = 300 watts.

Together, they add up to the 400 watts delivered by the mains.

CAUTION:
300 watts is an awful lot of power for a resistor to dissipate !
Those little striped jobbies can't do it.
It has to be a special 'power resistor'.
300 watts is even an unusually big power resistor.
If this story actually happened, it would be cheaper, easier,
and safer to get three more of the same kind of lamp, and
connect THOSE in series for 100 ohms. Then at least the
power would all be going to provide some light, and not just
wasted to heat the room with a big moose resistor that's too
hot to touch.

3 0

3 years ago

The amount of diffraction depends on the size of the obstacle and the wavelength of the wave.

tresset_1 [31]

I believe your answer is TRUE!
Hope this helps!:)

8 0

3 years ago

An object of irregular shape has a characteristic length of L = 0.5 m and is maintained at a uniform surface temperature of Ts =

goblinko [34]

Answer:

The value of the average convection coefficient is 20 W/Km².

Explanation:

Given that,

For first object,

Characteristic length = 0.5 m

Surface temperature = 400 K

Atmospheric temperature = 300 K

Velocity = 25 m/s

Air velocity = 5 m/s

Characteristic length of second object = 2.5 m

We have same shape and density of both objects so the reynold number will be same,

We need to calculate the value of the average convection coefficient

Using formula of reynold number for both objects

$R_{1}=R_{2}$

$\dfrac{u_{1}L_{1}}{\eta_{1}}=\dfrac{u_{2}L_{2}}{\eta_{2}}$

$\dfrac{h_{1}L_{1}}{k_{1}}=\dfrac{h_{2}L_{2}}{k_{2}}$

Here, $k_{1}=k_{2}$

$h_{2}=h_{1}\times\dfrac{L_{1}}{L_{2}}$

$h_{2}=\dfrac{q}{T_{2}-T_{1}}\times\dfrac{L_{1}}{L_{2}}$

Put the value into the formula

$h_{2}=\dfrac{10000}{400-300}\times\dfrac{0.5}{2.5}$

$h_{2}=20\ W/Km^2$

Hence, The value of the average convection coefficient is 20 W/Km².

7 0

4 years ago

What is the current when the voltage is 18 volts and the resistance is 6 ohms?

juin [17]

Voltage = current(I) * resistance (R)
V = 18
R = 6

18 = I * 6
I = 18/6 = 3 Amps or D

6 0

3 years ago

Read 2 more answers

needhelpp101 Why is the gravitational potential energy of an object 1 meter above the moon’s surface less than its potential ene

Vlad1618 [11]

If you remember the formula for potential energy,
then this question is a piece-o-cake.

<em>Potential energy = (mass) x (<u>acceleration of gravity</u>) x (height) .</em>

-- The object's mass is the same everywhere.
-- You said that the height is the same both times.
-- How about the acceleration of gravity ?

Compared to gravity on Earth, it's only 16.5 percent as much on the Moon.
So naturally, from the formula, you'd expect the Potential Energy to be less
on the Moon.

4 0

3 years ago