USE OF MACHINES A machine is a device or tool which allows a force (or effort) applied at one point to overcome a resisting force (or load) at another point.- a device that makes work easier, faster and more convenient.-comprises a stationary and moving parts combined together to generate mechanicalenergy Uses of Machines 1. as a force multiplier when load > effort2. as a speed multiplier in gears to reduce or increase speed3. as a displacement multiplier eg in a bicycle (wheel axle) na little movement of the pedal results to a large movement of the wheels.4. transforms mechanical energy to electrical5. to change the direction of a force eg in pulley systems downward force is used

to move a load upward.6. if a machine is frictionless, efficiency is equal to 100% and MA = V.R.

Classes Of Machines In Terms Of Performance

a. Generates mechanical energyb. Utilizes mechanical energyc. Transforms mechanical energy Need For Use Of Machines In Doing WorkMachines are used in all homes, schools, in offices, agriculture, industry etc to make work:i. Easierii. Quicker andiii. More convenient Repairs And Maintenance Of MachinesMachines are maintained to function well and last long1. Preventive Maintenance: This is the care or attention given to a machine to prevent

malfunctioning or damage Methods: by washing, cleaning the parts, polishing, greasing and oiling.

2. Predictive Maintenance 3. Corrective Maintenance: This is the care or attention given to a machine to correct

simple faults and prevent further damage to total breakdown.Method: by replacement or mending of the damaged parts

Repairs: This is done where preventive and corrective maintenance cannot ne used. AtThis point the machine has completely broken down.Effect Of Lack Of Maintenance:1. Rusting2. Low efficiency3. Total breakdown

DAMS AND ENERGY PRODUCTIONA dam: is an artificial barrier usually constructed across a stream or river channel to impound water. Examples Of Dams And Their Locationsi. Kainji dam located in Niger State ii. Shiroro dam located in Niger State iii. Zungeru dam located in Niger State iv. Bakori dam located in SokotoStatev. Asejire dam located in Oyo StateUses of dams in Nigeria Apart from hydro-electric power generation, dams are also used for:vi. Irrigationvii. Water supply.

How Electricity Is Produced From Dam:The hydroelectric power plant generates electricity from dam by harnessing the energyof water released from the reservoir to turn hydraulic turbines which rotate dynamo thatwould convert electrical energy to electrical developing voltage across the terminals.The power lines transmit the power to consumer within a regional power network.Advantages of Hydro Electrical Poweri. A renewable energy sourceii. Cheap and easy to maintainiii. Offers a significant contribution to development etc. Types of Dams1. Gravity dam2. Buttress dam3. Embankment archTo build a dam, the following are to be consideredi. Site testing ii. Site designiii. Site preparation

Assignment Describe the working principle of a named hydro electrical power plant