The Nature of Science Activity Build a battery-powered fan
Apparatus Solar panel, table lamp, switch, miniature electric motor, fan
Method 1. Connect the circuit as shown. 2. Shine the lamp on the solar panel and close the switch.
Fig. 10 A battery-powered fan.
3. Observe what happens. 4. Describe the energy changes that have taken place. Use the terms ‘energy input’ and ‘energy output’ in your description. 5. What function could this device perform?
30.4 Energy transfer and dissipation
Energy can be changed from one form to another, or transferred from one object to another. When this happens some of the energy is useful and some of the energy is not useful – it does not carry out what it was intended to do. This energy escapes and spreads out into the surrounding area, usually heating the air around it. It is so spread out that it is not useful anymore. This is called energy dissipation. The following examples demonstrate this.
1. A hammer hitting a nail When a hammer is held above a nail it has gravitational potential energy. When the hammer falls, gravitational potential energy is changed into motion energy. When the hammer hits the nail some of the motion energy is transferred to the nail, driving it down, and some is dissipated as heat and sound energy.
Motion energy
Gravitational potential energy
Heat/ Sound energy
2. A moving snooker ball If a snooker ball is gently tapped with a cue it will roll across the table and eventually come to a stop. The motion energy of the cue is transferred to the ball causing it to move. Some of this motion energy is converted to sound energy. The motion energy of the moving ball decreases until it comes to a stop. The motion energy of the ball is dissipated by the friction between the ball and the table. This friction causes the motion energy to be dissipated as heat energy.
Motion energy Sound energy Sound energy 328 Heat energy Motion energy Heat energy Fig. 12 The motion energy of the ball dissipates and the ball comes to a stop.
motion energy
No
Fig. 11 The energy changes when a hammer hits a nail.
