## Thermometer

For accurate readings, thermometer must be much smaller than the system, so that the energy the thermometer gains or loses does not significantly alter the energy content of the system. Thermometer can be calibrated by placing them in thermal contact with environments that remain at constant temperature. Eg. Pure melting ice(0°C) and pure boiling water (100°C) at 1 ATM. Problem …

## Thermal Contact

Thermal contact: Two objects are in thermal contact if energy can be exchanged between them. Two way process   Thermal Equilibrium(bodies at same temp): Two objects are in thermal equilibrium if there is no net exchange of energy when they are placed in thermal contact. Heat transfer will continue until thermal equilibrium is achieved.   Heat: The exchange of energy …

## Internal Energy

The internal energy is the total microscopic kinetic and potential energies of the particles (atoms and/or molecules) composing the system. $U = \sum E_{P} + \sum E_{K}$ U is a function of state(depends on state of system). T increase­ $\rightarrow$ Speed increases $\rightarrow$ microscopic KE ­increase $\rightarrow$ U ­increase To measure temperature quantitatively and objectively, a device is required.

## Equations relating to U, g and F

$U = m \phi$ $F_{g} = \, – \frac{dU}{dr}$ $g = \, – \frac{d \phi}{dr}$   $\frac{d \phi}{dr}$ is known as potential gradient. Gravitational field strength points in direction of decreasing $\phi$.

## Escape Speed

Escape speed is the minimum speed with which a mass should be projected from the Earth’s surface in order to escape Earth’s gravitation field. $V_{escape} \, = \, \sqrt{2g R_{E}}$ , where V is escape speed, g is gravitational field strength, R is radius of the Earth.   Derivation of Escape Speed From Earth We know that: \text{Total Energy at …

## Gravitational Potential

Gravitational potential, $\phi$, at a point in a gravitational field is the work done per unit mass, by an external force, in bringing the mass from infinity to that point. $\phi = \, – G \frac{M}{r}$ Units for $\phi$ is $J \, Kg^{-1}$. At infinity, $\phi$ is assumed to be zero.

## Gravitational Potential Energy

Gravitational potential energy, U of a point mass m, in a gravitational field, is the work done by an external force in bringing that point mass from infinity to that point. $U \, = \, G \frac{Mm}{r}$ Units of U is Joules (J). Reasons for a negative sign in the equation: Zero (reference point) for gravitational potential energy is set …