February 2025

Current electricity

By |2025-02-12T09:22:50+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

A simple circuit diagram A simple circuit diagram ZIMSEC O Level Combined Science Notes: Current electricity

  • When electricity flows from one point to another through a conductor this is known as electric current
  • Electric current when electricity flows from one point to another through a conductor
  • If an electric cell is used

    • […]

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Cells in a series

By |2025-02-12T09:39:03+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Cells in series Cells in series ZIMSEC O Level Combined Science Notes: Cells in a series

  • As already discussed cells give a voltage of around 1.5 V -2V
  • A lot of appliances required a higher voltage to function
  • Several cells can be joined together to giver larger voltages
  • This can be […]
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Fleming’s Left hand rule

By |2025-02-12T09:04:40+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Fleming's right hand rule Fleming’s right hand rule ZIMSEC O Level Combined Science Notes: Fleming’s Left hand rule

  • The direction in which a coil turns in influenced by the following factors:
  • the direction in which the current is flowing
  • the magnetic field
  • The direction of movement of a current carrying wire […]
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Joining trusses

By |2025-02-12T09:19:50+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Gang nails on a wooden truss. Gang nails on a wooden truss. Image credit naildesignart.biz ZIMSEC O Level Combined Science Notes:Joining trusses

  • In the real world various techniques are used to join trusses in ways that prevent joints from becoming points of weakness
  • Steel trusses are usually joined by welding […]
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Machines

By |2025-02-12T09:35:16+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Gears in a machine. Image credit wall.alphacoders.com Gears in a machine. Image credit wall.alphacoders.com ZIMSEC O Level Combined Science Notes: Machines

  • A machine is a device that makes work easier either by:
  • Reducing the effort (force) required to lift the load or
  • By changing the direction in which the effort is […]
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The siphon

By |2025-02-12T09:08:19+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Siphons being used for irrigation. Image credit wonderopolis.org Siphons being used for irrigation. Image credit wonderopolis.org ZIMSEC O Level Combined Science Notes: The siphon

  • In a siphon pressure is greatest in the lower end of the pipe
  • The pressure will cause the liquid to flow out
  • This reduces the pressure […]
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Diseases: Cholera

By |2025-02-12T09:26:00+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

People fetching contaminated water. Image credit mg.co.za People fetching contaminated water. Image credit mg.co.za ZIMSEC O Level Combined Science Notes: Diseases: Cholera

  • I usually spread by contaminated food and/or water
  • The cholera pathogen is a bacterium called Vibrio cholerae
  • It is an infectious disease
  • The pathogen lives and multiplies in the digestive […]
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Contraception: The use of spermicides

By |2025-02-12T09:43:53+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

Couple having dinner. Image credit singleblackmale.org Couple having dinner. Image credit singleblackmale.org ZIMSEC O Level Combined Science Notes:Contraception:Ways to prevent pregnancy

  • Spermicides are sperm killing chemicals

How it works

  • Are usually in the form of jelly cream placed into the vagina before sexual intercourse
  • The chemical kills spermatozoa

Effectiveness

  • 60-95%

Advantages

  • Does not require […]
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Protecting Water supplies

By |2025-02-12T09:10:19+02:00February 12th, 2025|Notes, O Level Science Notes, Ordinary Level Notes|

A protected well. Image credit totallandcare.org A protected well. Image credit totallandcare.org ZIMSEC O Level Combined Science Notes: Testing the purity of water

  • Most rural areas do not have access to running tap water
  • Their water comes from various sources including dams, wells, boreholes, springs
  • Some of these sources are produce […]
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