En una fundición hay un horno eléctrico con capacidad para fundir totalmente 540 kg de cobre. Si la temperatura inicial del cobr
1 answer:
Answer:
Q = 2.95*10^5 kJ
Explanation:
In order to calculate the energy required to melt the cooper, you first calculate the energy required to reach the boiling temperature. You use the following formula:
(1)
m: mass of cooper = 540 kg
c: specific heat of cooper = 390 J/kg°C
Tb: boiling temperature of cooper = 1080°C
T1: initial temperature of cooper = 20°C
You replace the values of the parameters in the equation (1):
Next, you calculate the energy required to melt the cooper by using the following formula:
(2)
Lf: melting constant of cooper = 134000J/kg
Finally, the total amount of energy required to melt the cooper from a temperature of 20°C is the sum of Q1 and Q2:
The total energy required is 2.95*10^5 kJ
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<h2>Answer:</h2>
(a) 3.18Ω
(b) 3.18Ω
<h2>Explanation:</h2>Let the two bulbs be A and B
Given;
= Resistance in bulb A = 3.0Ω
= Resistance in bulb B = 2.5Ω
Since the two bulbs are connected in parallel;
i. their effective resistance () is given by
=
+
---------------(i)
Substitute the values of and
into equation (i)
=> =
+
Solve for
= 1.36Ω
ii. voltage (potential difference), V, across them is the same;
Therefore we can get the total current (I) that will flow through them if the voltage to be supplied is 2.4V.
Use the Ohm's law;
V = I x R -----------------(ii)
Where;
V = voltage across them = 2.4V
I = total current flowing through them
R = their effective resistance = = 1.36Ω
Substitute these values into equation (ii) as follows;
2.4 = I x 1.36
I = 2.4 / 1.36
I = 1.76A
(a) Now get the value of R
Since the voltage across the two bulbs is 2.4V out of the 8.0V supplied by the source, then the remaining (8.0 - 2.4 = 5.6)V will pass across the resistor R.
Also, since the two bulbs make a series connection with the resistor R, the same total current (I = 1.76A) that flows through these bulbs will flow through the resistor R.
Therefore, to get the value of R, we use the relation
V = I x R ------------------------------(iii)
Where;
V = voltage across the resistor = 5.6V
I = current through the resistor = 1.76A
<em>Substitute these values into equation (iii)</em>
=> 5.6 = 1.76 x R
=> R = 5.6 / 1.76
=> R = 3.18Ω
Therefore, the value of R to be chosen in order to supply each bulb with a voltage of 2.4V is 3.18Ω
(b) The potential difference and voltage across refer to the same thing. Therefore, the value of R that would make the potential difference across each of the bulbs be 2.4V is the same as the one calculated in (a) which is 3.18Ω
Answer:
A=1
B=-2
Explanation:
Part A and B of the question wasn't given, however, I attached the relevant parts to solve this question as follows.
From part B as attached, it shows that the right option is C which is
2A+3B=-4
Substituting B with 3A-5 then we form the second equation as shown
2A+3(3A-5)=-4
By simplifying the above equation, we obtain
2A+9A-15=-4
Re-arranging, then
11A=-4+15
Finally
11A=11
A=1
To obtain B, we already know that 3A-5 so substituting the value of A into the above then we obtain
B=3(1)-5=-2
Therefore, required values are 1 and -2
