2016 - JAMB Physics Past Questions and Answers - page 5

41
Boiling occurs when the vapour pressure of a liquid is
A
At the evaporation point
B
Less than the atmospheric pressure
C
Greater than the atmospheric pressure
D
Equal to the atmospheric pressure
correct option: d
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42
If the magnification of a virtual image formed by an object 10cm from a convex less is 3, then the focal length of the lens is
A
10cm
B
20cm
C
25cm
D
15cm
correct option: d

M = (\frac{v}{u}) = 3 = (\frac{v}{30}). V = 30m

(\frac{1}{u}) + (\frac{1}{v}) = (\frac{1}{f}) = (\frac{1}{10}) - (\frac{1}{30}) = (\frac{1}{f})

(\frac{3 - 1}{30}) = (\frac{1}{f}

f = (\frac{30}{2}) = 15cm

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43
An electron in a hydrogen atom makes a transition from the ground level to the third level. If the energy at the ground level,calculate the energy at the third level.
[h = 6.6 x 10-34Js; f = 1015Hz]
A
1.41eV
B
1.71eV
C
1.61eV
D
1.51eV
correct option: d

E = (\frac{E_o}{n^2}) = (\frac{13.6}{3^2}) = (\frac{13.6eV}{9})

= 1.51eV

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44
In the diagram above, which of the following velocity-time graphs shows uniform acceleration of a body from rest?
A
C
B
D
C
B
D
A
correct option: c
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45
In the diagram above, the neutral point is at
A
R
B
X
C
S
D
P
correct option: b
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46
From the diagram above, the measuring accuracy of the micrometer screw gauge is
A
4.78mm
B
4.16mm
C
4.66mm
D
4.70mm
correct option: b
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47
In the diagram above, the direction of the force between N and S in the magnetic field is
A
MP
B
SN
C
NS
D
PM
correct option: c
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48
Which of the following statements is Not true about atoms?
A
Atom of different elements have different atomic weights
B
The mass of an atom is concentrated in the nucleus
C
An atom is made up of a nucleus and number of electrons
D
Atoms of all elements are identical
correct option: d
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49
The frequency of beats produced when two tunning forks of frequencies 258Hz and 270Hz are sounded close to each other
A
6Hz
B
264Hz
C
528Hz
D
12Hz
correct option: d

Beat = f2 - f1 = 270 - 258 = 12Hz

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50
Calculate the inductance of a coil of resistance 30\(\Omega\) connected to a 100V a.c source if the coil draws an r.m.s current of 2A
A
0.60H
B
2.50H
C
1.25H
D
0.04H
correct option: d
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