Answer:
R = 2481 Ω
L= 1.67 H
Explanation:
(a) We have an inductor L which has an internal resistance of R. The inductor is connected to a battery with an emf of E = 12.0 V. So this circuit is equivalent to a simple RL circuit. It is given that the current is 4.86 mA at 0.725 ms after the connection is completed and is 6.45 mA after a long time. First we need to find the resistance of the inductor. The current flowing in an RL circuit is given by
i = E/R(1 -e^(-R/L)*t) (1)
at t --> ∞ the current is the maximum, that is,
i_max = E/R
solve for R and substitute to get,
R= E/i_max
R = 2481 Ω
(b) To find the inductance we will use i(t = 0.940 ms) = 4.86 mA, solve (1) for L as,
Rt/L = - In (1 - i/i_max
)
Or,
L = - Rt/In (1 - i/i_max
)
substitute with the givens to get,
L = -(2481 Si) (9.40 x 10-4 s)/ In (1 - 4.86/6.45
)
L= 1.67 H
<u><em>note :</em></u>
<u><em>error maybe in calculation but method is correct</em></u>
Answer:
<em>Option D: It iwill actually warm the room</em>
<em></em>
Explanation:
<u>To complete your given question the available options are:</u>
A. It will cool the room very effectively
B. It will cool the room, but inefficiently
C. It will not change anything
D. It will actually warm the room.
This is a fun and somewhat tricky case. So, let us first understand a few principles in order to answer our question. To begin with<u><em>, the basic operating principle of the fridge is to take the hot air from the surrounding environment and cool it to the desired temperature in order to sustain all products inside the fridge</em></u>. It can also be thought as 'transferring' heat from the interior (i.e. inside the fridge) to the exterior (i.e. outside the fridge and into the surrounding).<em> In fact if you check the back of a fridge during operation, you will noticed a much higher temperature in that area. Which is due to the heat removed by the 'fridge operation system' in order to cool that interior air.</em> Therefore, this heat must transfer somewhere else, which typically ends up on the little fan located on the back of the fridge. We can also think of it in terms of the 2nd Law of Thermodynamics, which essentially tells us that the system (in this case the fridge and its surrounding)<em> MUST reach an Equillibrium.</em>
Therefore, when you do open the door of the fridge, you might initially (and for an instant almost) feel this 'cool' air coming out; thinking the surrounding air should soon cool down as well. But, due to our discussion above along with the principles of the 2nd Law of Thermodynamics, and considering the fridge operation over time,<em><u> the more cool air the fridge looses, the more the fridge system works to cool the air, thus the more the fans of the fridge work, which results to increasing heat getting 'dumped' by the fridge system and thus to the surrounding. </u></em>
<em></em>
<em>Consequently when you open the fridge door you will actually warm the room. (i.e. Option D). </em>
Answer:
g = 25 m/s²
Explanation:
Since, the balls meet at the exact instant when upward thrown ball reaches its maximum point. Therefore, applying 1st equation of motion to it, we get:
Vf₁ = Vi₁ + gt
where,
g = -g (for upward motion) = acceleration due to gravity at that planet = ?
t = time
Vf₁ = Final Velocity of Upward Thrown ball = 0 m/s (ball stops at highest point)
Vi₁ = Initial Velocity of Upward Thrown Ball = 100 m/s
Therefore,
0 m/s = 100 m/s - gt
gt = 100 m/s ------------- equation 1
Now, applying 3rd equation of motion for the height covered:
2(-g)h₁ = Vf₁² - Vi₁²
h₁ = 10000/2g
Now, we apply 2nd equation of motion to second ball moving downward:
h₂ = Vi₂t + (0.5)gt²
where,
h₂ = height covered by second ball at the time of meeting
Vi₂ = initial velocity of second ball = 0 m/s (since, it starts from rest)
Therefore,
h₂ = (0)(t) + (0.5)gt²
h₂ = (0.5)gt²
Now, it is clear from the given condition, that when the two balls meet, the sum of distance covered by both the balls will be equal to 400 m. Therefore,
h₁ + h₂ = 400 m
using values:
10000/2g + (0.5)gt² = 400
10000 + g²t² = (400)(2g)
using equation 1:
10000 + (100)² = 800g
g = 20000/800
<u>g = 25 m/s²</u>
Power (P)= Voltage (V)* Current (I)
So I=P/V=12/9
I=1.3A
*This is a common answer of mine*
Hope this helps.