Find the resistance (in kΩ) that must be placed in series with a 25.0 Ω galvanometer having a 50.0 µA sensitivity (the same as the one discussed in the text) to allow it to be used as a voltmeter with a 0.215 V full-scale reading.

4.28 kΩ

Explanation:

A galvanometer is used for measuring small currents. A galvanometer can be converted to a voltmeter by connecting a high resistance or multiplier in series with the galvanometer. In the given question:

The sensitivity of the galvanometer is 50×10-6A. The voltage across the galvanometer (V1) is 1.25×10-3 V as shown in the solution attached. This is then subtracted from the expected full scale reading of the voltmeter to obtain the potential difference across the multiplier as shown. This voltage across the multiplier is then used to obtain the multiplier resistance as shown.

First of all the kinetic energy is when the particles move in continuous random motion.

If the temperature is high the colliding particles will collide more. and if the temperature is low the colliding particles will collide less.

Low temperature result in low kinetic energy 
High temperature result in high kinetic energy

Absolute zero is the point where where all molecules have no kinetic energy. It is a theoretical value (it has never been reached).

The Kelvin temperature scale is based on absolute zero being the lowest possible temperature that could theoretically be reached. That is why there is no such thing as a negative Kelvin temperature value.