Waec may/June 2018 Physics Practical Answers

Phy - Pract - Answers


1axi)
Precautions
Take Any Two

i ) I avoided conical oscillation
ii) I avoided drought
iii ) I avoided parallax error in taking reading from the metre rule
iv ) I avoided zero error in taking reading from the stop watch

2aix)
PRECAUTIONS
I) experiment must be carried out in a dark room
II) lens, screen and object must be in line

3aix)
- *precautions*-
take any two
i ) I removed key when reading is not taking
ii) I ensured tight connections at the terminals
iii ) I avoided parallax error when taking reading from the ammeter .

1)
Tabulate
s/n= 1,2,3,4,5
L(cm)= 130,110,90,70,50
T1(sec)= 45.70,42.00,38.00,33.10,28.70
T= 2.29,2.10,1.90,1.66,1,44
T^2= 5.22,4.41,3.61,2.74,2.06
L=100,80,60,40,20

1)
-precautions-
Take Any Two
i)I avoided conical oscillation
ii)I avoided drought
iii)I avoided parallax error in taking reading from the metre rule
iv)I avoided zero error in taking reading from the stop watch


3)
Tabulate

3)
-precautions-
take any two
i)I removed key when reading is not taking
ii)I ensured tight connections at the terminals
iii)I avoided parallax error when taking reading from the ammeter.

1b i.
focal length of an object is 20means that the distancebetween the optical centre or middle of the lens and its principal focus is 20cm


1bii.
given that u=x f=20 v=5

using the mirror formula
1/u + 1/v = 1/F

1/x + 1/5 = 1/20

multiply through by the LCM
1/X x 5 + 1/5 x 5 = 1/20 x 5

5/x =5/20
5/x =1/4
taking the reciprocal
x/5 =4/1

cross multiply
X x 1 = 5 x 4
X =20

















1xii)
-precautions-
Take Any Two
i)I avoided conical oscillation
ii)I avoided drought
iii)I avoided parallax error in taking reading from
the metre rule
iv)I avoided zero error in taking reading from the
stop watch
pls keep calm we will update
the rest soon
======================

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
=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 arebr /> -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

2bi)
The 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)
==============================

3)
Tabulate
s/n 1,2,3,4,5
D(cm) 25,35,50,65,80
I(A) 1.99,1.75,1.55,1.44,1.36
I^(A-¹) 0.530,0.571,0.645,0.694,0.735
Lo(j^) -0.2984,-0.2434,-0.1904,-0.1586,-0.1337

3viiii)
slope Dvertical/Dhorizontal
=1.41-1.00/80-25
=0.4/55
S=0.00727

3x)
from the graph C=32cm
3xi)
K=c/2=33/2=16cm

3xii)
-precautions-
take any two
i)I removed key when reading is not taking
ii)I ensured tight connections at the terminals
iii)I avoided parallax error when taking reading
from the ammeter.

3bi)
At I=1.5A,1/I=1/1.5=0.67A-¹
Log(I-¹) = Log 0.67=0.17

3bii)
i)length - longer wires have greater resistance.
ii)thickness - smaller diameter wires have
greater resistance.