Real and confirmed Neco 2017 Marketing Essay and obj Answers

2bi)
he characteristics of imaged formed are :
i)It is virtual
ii) It is enlarged or magnified i.e. twice or two times bigger as the object(m=2)
2bII) The concave mirror ,mounted in its holder ,is moved to and fro in front of the until a sharp image of the cross wire of the ray box is formed on the screen adjacent to the object .The distance between the mirror and the screen was measured as 30.1cm.Since the radius of the curvature r,=2fo ,then half this distance is the focal length of the mirror fo .Thus focal length was determined to be 15.05cm approximately 15cm
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(3aiii)
Vo=0.35V
TABULATE
S/N:1,2,3,4,5,6
R(ohm):1.0,2.0,3.0,4.0,5.0,6.0
V(v):1.40,1.65,1.80,2.00,2.10,2.15
R^-1(ohm^-1):1.000,0.500,0.333,0.200,0.1
V^-1(v^-1):0.714,0.606,0.556,0.500,0.476,
(3aiv)
DRAW THE GRAPH of V^-1(v^-1) against R^-1
(3av)
Slope=change inV^-1/Change inR^-1
=(7.6-4.3)/(0.84-0.10)
3.3/0.74
=4.460
(3avi)
Intercept=0.385
(3avii)
I=0.385
I^-1=(0.385)^-1
=2.597
(3aviii)
-I ensured tight connections
-I avoided error due to parallax when reading the voltmetre
-I ensured the key is opened after each reading to prevent the cell from running down
(3bi)
The potential difference between two points in an electric circuit is the work done when a coulomb of charge passes between the points in an electric circuits
(3bii)
E=I(R+r)
where E=e.m.f of the cell
Therefore E=IR+Ir=V+Ir
Where :
V=IR=P.d lost across the external resistance of the cell
Ir=Pd lost across the internal resistance of the cell
E=e.m.f=workdone across external resistance of the cell
Since V=IR is the workdone across the external resistance R only can be other than V

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