State the energy changes in the following cases while in use:
(a) loudspeaker
(b) a steam engine
(c) microphone
(d) washing machine
(e) an electric bulb
(f) burning coal
(g) a solar cell
(h) bio-gas burner
(i) an electric cell in a circuit
(j) a petrol engine of a running tar
(k) an electric toaster
(l) a photovoltaic cell
(m) an electromagnet.

Hint:Conversion of energy from one form to another form is called energy conversion. There are different forms of energy. Energy is found in six forms. They are chemical, thermal, mechanical, radiant, electrical and nuclear energy. Energy can be transferred in three different ways called conduction, radiation and convection.

Complete answer:
The most common type of energy conversion is the conversion of potential energy into kinetic energy and kinetic energy into potential energy. Energy conversion is very crucial for life on earth. Every activity in our day to day life involves energy conversion.

The energy changes are as follows:
(a) Electrical energy into sound energy
(b) Heat energy into mechanical energy
(c) Sound energy into electrical energy
(d) Electrical energy to mechanical energy
(e) Electrical energy into light energy
(f) Chemical energy to heat energy
(g) Light energy into electrical energy
(h) Chemical energy into heat energy
(i) Chemical energy into electrical energy
(j) Chemical energy to mechanical energy
(k) Electrical energy into heat energy
(I) Light energy into electrical energy
(m)Electrical energy into magnetic energy

Note:We can find energy conversion in many daily life activities. Energy is very essential to all living organisms. The source of all the energy available on Earth is the sun. The common forms of energy that we use in our daily life are chemical energy, electrical energy in the form of food, fuels, etc. Energy can be simply defined as the ability to cause change.