WAEC GCE 2016 PHYSICS ALTERNAT IVE TO PRACTICA L ANSWERS – NOV/DEC EXPO

1b)
Relative density, or specific gravity, is the ratio
of the density (mass of a unit volume) of a
substance to the density of a given reference
material. Specific gravity usually means relative
density with respect to water.
1bii)
given volume of solid immersed
Vsi =1/2*30cm³
=15cm³
Density of liquid (water)ew= 1g/cm³
Acceleration due to gravity, g = 10m/s²
Upthrust, U= eVsi g U= 1000*(15*10^-6)*10
U=15*10-²
U=0.15N
Weight of solid =mg
=EsVs g
given: Es=2.4g/cm³ (2400kg/m³)
Vs=30cm (30*10^-6 m³)
g=10m/s²
Weight, w=30*10^-6*2400*10
=72*10-²
=0.72N
Reading on spring balance =W-U
=0.72-0.15
=0.57N
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2bi)
-It is used for Magnifying glass:
For a magnifying glass to work, the object is
placed at the focal point such that the image
produced is magnified, upright and virtual.
- It is used in aSlide projector:
A projector essentially uses a convex lens to
form on a screen a real, magnified and inverted
image of the slide or film. The slide, being the
object, is positioned between the j and 2f from
the lens.
3b)Internal resistance of a cell is the resistance
within a battery, loadedextra.com or other
voltage source, that causes a drop in the source
voltage when there is a current. There is,
therefore, actual reduction in the electromotive
force of the cell , as well as an increase in
internal resistance.
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