# Questions tagged [energy]

Energy is the conserved quantity associated to time-translation invariance and represents the work a system is capable of doing. Use this tag for questions about energy, and consider adding the [energy-conservation] tag if it is specifically about its conservation.

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### Is it Possible to Directly Measure Energy?

Would it be possible to measure energy directly in joules instead of measuring what effect energy has on something? Say for example you have a car of known weight traveling a speed v. To get the car's ...
26 views

### What is the difference between the specific heat capacities of water under isobaric and isochoric conditions

Can the difference of specific heat capacity of water under isochoric and isobaric conditions be explained in terms of the internal energy of the system? Most of the videos I have watched base their ...
21 views

### The expectation value of the energy of the general wave function in the infinite square well

We know in the infinite square well that the general solution is a linear combination of the stationary states ( states with definite energy eigenvalues). Also the measurement of the energy for that ...
51 views

### Is the heat dissipated by a resistor given by $I^2RT$ or $(V^2/R)T$? [closed]

Is the heat dissipated by a resistor given by $H = I^2RT$ or $H=(V^2/R)T$? In other words, if the resistance is reduced by a quarter, will the dissipated heat increase or decrease? The two formulas ...
2k views

### Why is maximal kinetic energy lost in a perfectly inelastic collision?

A perfectly inelastic collision is one where both of the colliding objects stick together and move as one. My questions is, why, of all possible combinations of final velocities that conserve momentum,...
600 views

### Work term in First Law of Thermodynamics

The first law states that $\text{d}Q = \text{d}W + \text{d}U$ where $\text{d}W$ is the work done by the system on the surroundings. As far as I remember from my chemistry courses,first law in ...
184 views

### Why work done is needed when other physical quantities are available?

I have some question about work done. I understand the mathematical ways and examples which are floating all over on internet & books. But all these information not clearing the concepts of work ...
41 views

### Mechanism of heating during deformation [duplicate]

When a metal or rubber is bent and deformed, it heats up. What is the reason for this? I know that when deforming it, work is done on the object. If the object is perfectly elastic, all of the energy ...
29 views

### What is the physical meaning of ΔG = q(irr) - q(rev)?

Why is change in enthalpy ΔH equal to heat exchanged following whether reversible or irreversible path whereas TΔS is equal to the heat that would be exchanged if the process was reversible? What is ...
103 views

### What makes an electron jump down to lower energy level?

While I can easily grasp the mechanism of energy absorption by the atom system resulting in a jump of the electron to a higher energy level, i.e. receiving energy from the outside in the form of a ...
78 views