# Tag Info

Accepted

### Currently self-studying QFT and The Standard Model by Schwartz and I'm stuck at equation 1.5 in Part 1 regarding black-body radiation

It just a clever use of the geometrical series: $$\frac{1}{1-q} = \sum_{j=0}^\infty q^j$$ which is valid for any real number $q<1$. Here $q = e^{-E_n\beta} \equiv e^{-\hbar\omega_n\beta}$. As long ...
• 6,328
Accepted

### Probability of observing harmonic oscillator at a particular position

When dealing with continuous distributions, one should make difference between probability and probability density. Probability of hitting any specific point of a continuous distribution is zero, ...
• 37.4k

• 2,733
1 vote

### Is it true that the Poynting theorem $P=E\times H$ is quite valid for DC circuits?

If something is stationary, it is a special case of being time-varying (with time derivative equals zero). So there is no need to repeat the proof of Poynting's theorem in the narrow sense of ...
• 7,114
1 vote
Accepted

### How can we say potential or chemical energy is part of an object?

In a detailed microscopic model of a system of particles, we can distinguish energy of the microscopic EM field (EM energy), and the other energy (due to mass and kinetic energy of massive particles). ...
• 27.9k
1 vote

### Non-Work energy conversion

Work is a more general concept than a force acting through a distance. The mechanics branch of physics primarily addresses work for a point particle, or a rigid body, for which there is no change in ...
• 6,188

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