2018 - JAMB Physics Past Questions and Answers - page 9
81
Which of the following instruments is most suitable for measuring the outside diameter of a narrow pipe in a few millimeters in diameter?
A
Pair of calipers
B
Meter rule
C
Micrometer screw gauge
D
Tape rule
correct option: c
Users' Answers & Comments82
Electrical power is transmitted at a high voltage rather than a low voltage because the amount of energy loss is due to
A
Heat dissipation
B
Production of eddy currents
C
Excessive current discharge
D
Excessive voltage discharge
correct option: a
The primary reason that power is transmitted at high voltages is to increase efficiency. As electricity is transmitted over long distances, there are inherent energy losses along the way. High voltage transmission minimizes the amount of power lost as electricity flows from one location to the next. ~ Betaengineering.com
Users' Answers & Comments83
If the focal length of a camera is 20cm, the distance from the film at which the lens must be set to produce a sharp image of 100cm away is
A
17cm
B
20cm
C
25cm
D
100cm
correct option: a
F = 20cm
V = 100cm
U = ?
\(\frac{1}{U}\) + \(\frac{1}{V}\) = \(\frac{1}{F}\)
\(\frac{1}{20}\) + \(\frac{1}{100}\) = \(\frac{1}{F}\)
5 + \(\frac{1}{100}\) = \(\frac{1}{F}\)
F = \(\frac{100}{6}\)
= 16.7cm
= 17cm