Answer:
answer a) 2
Explanation:
Assuming stationary state, following Fourier's law:
Q = A*k* dT/dL
where Q= heat flow , A= cross sectional area, dT/dL= temperature gradient along the bar
if the cross sectional area is doubled , then the gradient is the same ( since the heat sources do not change in temperature or position , and the length of the bar is the same). Since the gradient is same , the temperature is the same under stationary conditions , then we can assume k remains constant in the cross section.Therefore
Q₁= A₁*k* dT/dL
Q₂= A₂*k* dT/dL
dividing both equations
Q₂ / Q₁ = A₂/A₁ = 2
then the correct answer is a)
Note:
Since the cross sectional area is doubled, then heat loss to the surroundings will be
Q loss= h* A exposed * ΔT
then
Q loss₂ / Q loss ₁ = A exposed ₂/ A exposed ₁
for a circular cross section or a squared cross section
A exposed ₂/ A exposed ₁ = √2
then
Q loss₂ / Q loss ₁ = √2
therefore we did not take into account the increase in heat loss due to the increased in exposed area to the environment
Answer:
356.33 J
Explanation:
Energy: This can be defined as the ability or the capacity to do work. The S.I unit of Energy is Joules (J).
The Energy stored in a capacitor = 1/2CV²
E = 1/2CV².............................. Equation 1.
Where E = Energy stored in a capacitor, C = capacitance of the capacitor, V = potential difference across the plates of the capacitor.
Given: C = 10.5 μF = 10.5×10⁻⁶ F, V = 8250 V.
Substitute into equation 1
E = 1/2(10.5×10⁻⁶)(8250)²
E = 357.33 J.
Thus the energy stored in the defibrillator = 356.33 J
It can't be less than 250 N or the cart wouldn't move at all. That means there is only 1 answer. It's between not enough info or 250 N. The answer is 250 N. If it was any more, there would be acceleration.
The efficiency of the appliance is 0.62 (62%)
Explanation:
The relationship between the power of the appliance and the energy used by it is
where
P is the power
E is the energy transferred in input
t is the time elapsed
For this appliance,
P = 7 W
So, in t = 42 s, the energy transferred in input is
We are told that the useful energy in output however is
Therefore, the efficiency of the appliance is
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Elements are made of atoms, which are particles that represent the most basic form of an element.<span> An atom is the smallest particle of an element and cannot be further divided without becoming a less complex particle; in fact, the word 'atom' comes from the Greek word "atomos," meaning 'indivisible'.</span>