Compare brakes and dynamometers (two points).
Brakes : A brake is a device by means of which artificial frictional resistance is applied to a moving machine member, in order to retard or stop the motion of a machine.
Types : Hydraulic brakes
1.Electric brakes 2.Mechanical brakes.
The brake absorbs either kinetic energy of the moving member or potential energy given up by objects being lowered by hoists, elevators etc.
The energy absorbed by brakes is dissipated in the form of heat.
This heat is dissipated in the surrounding air (or water which is circulated through the passages in the brake drum) so that excessive heating of the brake lining does not take place.
Dynamometers : A dynamometer is a brake but in addition it has a device to measure the frictional resistance.
Knowing the frictional resistance, we may obtain the torque transmitted and hence the power of the engine.
Types : 1. Absorption dynamometers, and 2. Transmission dynamometers