Monday, 5 June 2017

Pratical physics neco

NECO 2017 PHYISCIS PRACTICAL ANSWERS
(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):1.000,0.500,0.333,0.200,0.167
V^-1(v^-1):0.714,0.606,0.556,0.500,0.476,0.465
(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 VVfVVf
2ai)
fo=15cm
2av)
a=60.00cm
b=20.00cm
Hence L=a/b=60.00/20.00
L=3
2avi)
TABULATE
S/N:1,2,3,4,5
b(cm):20.00,25.00,35.00,40.00
a(cm):60.00,37.50,30.00,26.25,24.00
L=a/b:3.00,1.50,1.00,0.75,0.60
2avii)
Slope=Change in L/Change in a
=(3-0.25)/(60-18.6)
=2.75/41.4
=0.006642
2aviii)
S^-1=1/S
=(1/0.0066425cm)
S=15.05
S=15cm
2aix)
PRECAUTIONS
-I ensured that all apparatus are in straight line
-I avoided error due to parallax when reading the metre rule
-I avoided zero error on the metre rule
2bi)
u=10cm
f=15cm
Using 1/v+1/u=1/f
1/f-1/u=1/v
1/v=1/15-1/10
1/v=(2-3)/30
1/v=-1/30
v=-30cm
The characteristics of image formed are:
-It is virtual
-It is enlarged and magnified ie twice or two times as big as the object m=2
2bii)

The concave mirror mounted in its holder is moved to and fro in front of the screen until a sharp image of the cross wire of the ray box is formed on the screen adjacent of the object.The distance between the mirror and the screen was measured as 30cm since the radius of curvature r=2fo then half is distance


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