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3 years ago

6

Electrical Safety: What should you do to a hot plate before turning it on? More than one answer may be correct. Check that the l

ead does not trail in liquid. Check the cable for exposed wires. Position in a stable place away from places where it could be knocked over. Wipe any oil residues off the hot plate.

1 answer:

solniwko [45]3 years ago

8 0

Answer and Explanation:

Before turning a hot plate on, one should consider these points:

Check for the leads and ensure they does not trail in liquid.
The cable should be checked for any exposed wire before turning on in order to prevent any shock.
Any oil residue should be wiped off of the hot plate to ensure its longevity.
It should be placed in a stable place in order to ensure safety against any hazard.
Thus all the above mentioned points are correct to ensure safety.

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The study of the human perception of sound is called psychoacoustics.

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A piston–cylinder device initially contains steam at 3.5 MPa, superheated by 5°C. Now, steam loses heat to the surroundings and

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<u>Answer :</u>

(a) The Initial temperature of the steam is 247.557°C

(b) The enthalpy change per unit mass of the steam is -1771 kJ/kg

(c) The final pressure is 1555 kPa, and the liquid vapor mixture contains small mass of vapor.

<u>Explanation :</u>

From the given statements, we know

Initial steam pressure ( $P_1$ ) = 3.5 MPa

Degree of Super heat = 5°C

Saturation Temperature ( $T_s_a_t$ ) = 242.557°C [From Steam Table]

Now, the Initial temperature ( $T_1$ ) of steam is given by-

$T_1$ = $T_s_a_t$ + Degree of Superheat

= 242.557 + 5 = 247.557°C

(b)To find: The enthalpy change per unit mass of the steam is

We know enthalpy (h) change is given by

Δh = $h_2$ – $h_1$

From steam Table, properties of the gas at state 1 and state 2

$h_1$ = 2821.1 kJ/kg

$h_2$ = 1049.7 kJ/kg

On substituting the values, we get

or, Δh = 1049.7 - 2821.1 = -1771 kJ/kg

(c) To Find: The final pressure of the liquid vapor mixture contains small mass of vapor.

We find that the gas at the final position, i.e., at position 3

Final Temperature ( $T_3$ ) = 200°C [Given] ……………………………..(1)

Specific Volume ( $v_3$ ) = Specific Volume ( $v_2$ ) = 0.00123 $m^3$ /kg ….....(2)

Using steam table for corresponding values of (1) and (2), we get

Final Pressure $P_3$ = 1555 kPa

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B) Decrease

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3 years ago

Determine the frequency of the 2nd harmonic of a spring that has a 3rd harmonic resonance of f3=512 Hz.

Elena L [17]

Answer:

1) 341 Hz

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And so, the frequency of the 2nd harmonic is:

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