Answer:
60 J
Explanation:
Given That
Coefficient of performance, CoP = 4.2
Quantity of heat of the refrigerator, Q = 250 J
Work done by the refrigerator, W = ?
First, it should be noted that the Coefficient of Performance can be said to be, the ratio of the Heat required to the Work done by the system. Mathematically written as,
CoP = Q / W
Since we are already given the values from our question, we can plug it in as it's a pretty straightforward question
4.2 = 250 / W, making W subject of formula, we have
W = 250 / 4.2
W = 60J
Thus, the Work done by the refrigerator is 60 J
Answer:0.69
Explanation:
Coefficient of kinetic friction=f/R=61.8/90=0.69
To solve this problem it is necessary to apply the second derivative of the function to find the maximum time reference and thus calculate the maximum voltage.
With the maximum voltage by Ohm's Law it is possible to find the maximum current.
Ohm's law defines that
E = I*R
Where,
I = Current
R= Resistance
On the other hand by faraday studies and the potential can be expressed at the rate of change of the electric flow, that is

Replacing with our values we have that


The second derivative is

When E' = 0 we have a Maximum, then
0 = -36t+36
t = 1
Therefore when the time is 1s E has a Maximum, replacing at the function



Then the maximum current will be given by



Therefore the maximum current induced in the ring is 6.42A