1991 - JAMB Physics Past Questions and Answers - page 4
31
An insulated rod when rubbed with a material acquires
A
a negative charge if it is made of glass and rubbed with silk
B
no charge if it is made of glass and rubbed with fur
C
no charge if it is made of copper and rubbed with silk
D
a positive charge if it is made of copper and rubbed with fur
correct option: b
Users' Answers & Comments32
The function of the system of granulated carbon mixed with manganese (IV) oxide in a Letanche cell is to
A
increase the e.m.f. of the cell to 2.0V
B
prevent local action in the cell
C
prevent polarisation in the cell
D
make the cell black and hence a good radiator
correct option: c
Users' Answers & Comments33
A moving coil galvanometer of 300\(\Omega\) resistance gives full scale deflection for 1.0mA. The resistance R, of the shunt that is required to convert the galvanometer into a 3.0A ammeter is
A
899.70\(\Omega\)
B
10.00\(\Omega\)
C
0.10\(\Omega\)
D
0.01\(\Omega\)
correct option: c
Users' Answers & Comments34
Which of the following obeys Ohm's Law?
A
Glass
B
Diode
C
All electrolytes
D
All metals
correct option: d
Users' Answers & Comments35
An equipment whose power is 1500W and resistance is 375 ohms would draw a current of
A
0.10A
B
2.00A
C
4.00A
D
77.5A
correct option: b
P = I2R \(\Rightarrow\) I = \(\sqrt\frac{P}{R}\)
I = \(\sqrt\frac{1500}{375}\)
= 2A
Users' Answers & CommentsI = \(\sqrt\frac{1500}{375}\)
= 2A
36
To convert an alternating current dynamo into a direct current dynamo, the
A
number of turns in the coil is increased
B
strength of the field magnet is increased
C
slip rings are replaced with a split ring commutator
D
coil is wound on a soft iron armature
correct option: c
Users' Answers & Comments37
If a current carrying coil is mounted on a metal frame, the back e.m.f. induced in the coil causes
A
inductance
B
eddy currents
C
elecro-magnetism
D
dipole moment
correct option: b
Users' Answers & Comments38
The electrochemical equivalent of platinum is 5.0 x 10-7kgC-1 to plate-out 1.0kg of platinum, a current of 100A must be passed through an appropriate vessel for
A
5.6 hours
B
56 hours
C
1.4 x 104 hours
D
2.0 x 104 hours
39
which of the following statements are TRUE of isotopes? i. isotopes of an element have the same chemical properties because they have the same number of electrons. ii. isotopes of elements are normally separated using physical properties. iii. isotopes of an element have the same number of protons in their nuclei.
A
i and ii only
B
i and iii only
C
ii and iii only
D
i, ii, and iii
correct option: b
Users' Answers & Comments40
When an atom loses or gains a charge, it becomes
A
an electron
B
an ion
C
a neutron
D
a proton
correct option: b
Users' Answers & Comments