2013 - JAMB Physics Past Questions and Answers - page 5
41
Induced emfs are best explained using
A
Ohm's law
B
Faraday's law
C
Colomb's law
D
Lenz's law
correct option: d
Users' Answers & Comments42
If a current of 2.5A flows through an electrolyte for 3 hours and 1.8g of a substance is deposited, what is the mass of the substance that will be deposited if a current of 4A flows through it for 4.8 hours?
A
2.4g
B
3.2g
C
4.6g
D
4.8g
correct option: c
First let's find z
z = \(\frac{M}{It}\)
z = \(\frac{1.8}{2.5 \times (3 \times 60 \times 60)}\)
Therefore, the new M equals
M = zIt
M = \(\frac{1.8 \times 4 \times 4.8 \times 60 \times 60}{2.5 \times 3 \times 60 \times 60}\)
M = 4.6g
Users' Answers & Commentsz = \(\frac{M}{It}\)
z = \(\frac{1.8}{2.5 \times (3 \times 60 \times 60)}\)
Therefore, the new M equals
M = zIt
M = \(\frac{1.8 \times 4 \times 4.8 \times 60 \times 60}{2.5 \times 3 \times 60 \times 60}\)
M = 4.6g
43
Calculate the energy of the third level of an atom if the ground state energy is - 24.8eV
A
-9.20eV
B
-8.20eV
C
-2.75eV
D
-1.75eV
correct option: c
\(E_3 = \frac{E}{n^2}\)
\(E_3 = \frac{-24.8}{3^2}\)
\(E_3 = 2.75eV\)
Users' Answers & Comments\(E_3 = \frac{-24.8}{3^2}\)
\(E_3 = 2.75eV\)
44
In photo-emission, the number of photo-electrons ejected per second depends on the
A
frequency of the beam
B
work function of the metal
C
threshold frequency of the metal
D
intensity of the beam
correct option: c
Users' Answers & Comments45
The particle nature of light is demonstrated by the
A
photoelectric effect
B
speed of light
C
colours of light
D
diffraction of light
correct option: a
Users' Answers & Comments46
The energy of a photo having a wavelength of 10-10m is
(h= 6.63 x 10 -34Js, c =3.0 x 10 8ms-1)
(h= 6.63 x 10 -34Js, c =3.0 x 10 8ms-1)
A
2.0 x 10 -15J
B
1.7 x 10 -13J
C
2.0 x 10 -12J
D
1.7 x 10 -12J
correct option: a
E = \(\frac{hc}{\lambda}\)
E = \(\frac{6.63 \times 10^{-34} \times 3 \times 10^18}{10^{-10}}\)
E = 2 x 10-15J
Users' Answers & CommentsE = \(\frac{6.63 \times 10^{-34} \times 3 \times 10^18}{10^{-10}}\)
E = 2 x 10-15J
47
The bond between silicon and germanium is
A
dative
B
covalent bond
C
trivalent
D
ionic
correct option: b
Users' Answers & Comments