### Chapter #7Work , Power and Energy : Short Q/A / C.R.Q's

Q. If a cup it dropped and break into pieces then discuss the energy change.
Ans. There will be the following energy changes
* Potential energy of cup changes into kinetic energy
* The kinetic energy that converts into heat and sound energy.
* due to breaking the energy in the bonds of cup atoms breast and also converts into heat.

Q. A man standing still talking to his friend and the running engine of a stationary car. Write the similarity between two w.rt Work?
Ans. With respect to work Both are very much similar because A man standing still talking to his friend is not doing any work according to the physics and also the running engine of a stationary car is not doing work because the car is stationary.

Q.When a rocket re-enters the atmosphere, its nose become very hot .Where does this heat energy come from?
Ans. When the rocket comes back in to the atmosphere its nose become hot due to the work done against friction. As we know that the atmosphere is the upper sphere of gases on the earth. so the rocket having the potential energy changes some of its potential energy in the work done against friction that why nose becomes hot.

Q. Why we become physically tired when we push against a wall, fail to move it and therefore don’t work on the wall?
Ans. In this case although the wall does not changes its position so the work is zero but during the application of the force our muscles expand and contracts .This expansion and contraction of the muscles utilizes the energy so we become physically tired.

### COMMON COLLECTOR CONFIGURATION OF A TRANSISTOR

COMMON COLLECTOR CONNECTION

In  this  configuration  the  input  is  applied  between the  base  and  the  collector and  the  output  is  taken  from  the  collector  and  the  emitter.  Here  the  collector  is common to both the input and the output circuits as shown in Fig.

Common Collector Transistor Circuit

In  common  collector  configuration  the  input  current  is  the  base current  IB  and  the output current is the emitter current IE. The ratio of change in emitter current to the  change in the base current is called current amplification factor.

It is represented by

COMMON COLLECTOR CIRCUIT

A test  circuit  for determining the  static characteristic  of an NPN transistor is shown in Fig. In this circuit the collector is common to both the input and the output circuits.   To   measure   the   base   and   the   emitter   currents,   milli   ammeters   are connected in series with the base and the emitter circuits. Voltmeters are connected   across the input an…