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Things to know for 04-05 Semester #2 pg2
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  • Fixed pulley 

  • Does not multiply force.
  • Changes the direction of the effort force.
    • Mechanical advantage is equal to one.

  • Movable pulley

Multiplies effort force but cannot change direction of the effort force.

Mechanical advantage is the effort distance divided by the resistance distance.

 

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  • wheel and axleWheel and axle  a lever that rotates in a circle around an axle.
    • Two wheels of different sizes connected - the axle being the smaller wheel.
    • EF applied to the wheel is multiplied at the axle.

 
  • Electricity
    • Properties and types of electric charge (positive, negative, what repels, what attracts)
    • Electrostatic charge
    • how objects become charged
    • rubbing, contact with a charged object, induction
    • (gaining electrons or losing electrons, moving electrons within the object)
    • Electrical force
    • Coulomb’s Law of electrostatics: dependence on charge and distance
    • Similarities and differences from gravitational force
    • Electric field
    • electric potential (potential energy per unit charge, units: volts)
    • electric potential difference (difference in electric potential between two points, units: volts)
    • electric current (units: Amperes (or Amps))
    • electric circuits
    • how to make (what must be the case to have an electric circuit?)
    • definition of resistance (units: Ohms)
    • Ohm’s Law
    • Series and parallel circuits (how they work, how to find V, I, R, P in different circuits)
    • How to find equivalent resistance of complex (more than one resistor) circuits
    • Electric power (P = IV = energy/time)
    • Which is more dangerous- high voltage or high current flow?
    • conductors, insulators, semi-conductors
  • Magnetism
    • magnetic poles (north, south, what repels, what attracts)
    • magnetic force, magnetic field, dependence of force on distance
    • Magnetic domains, what makes an object "magnetic"
    • Ferromagnetic, paramagnetic, and diamagnetic materials
  • Relationship between electric and magnetic fields
    • moving charges (current) produce a magnetic field (electromagnet)
    • magnetic fields affect moving charges
    • changing magnetic fields induce a current (electromagnetic induction)
    • light (electromagnetic radiation) is a self-propagating electromagnetic disturbance
  • Important general concepts:
    • Like charges (or magnetic poles) repel, opposite charges (or magnetic poles) attract
    • An object in which a charge has been induced behaves like a charged object even though there is
    • no net positive or negative charge on the object.
    • The concept of a force field helps us quantify the effect of forces which act at a distance for any
    • point in space.
    • Electric fields and magnetic fields are intimately related.

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