2001 - WAEC Physics Past Questions and Answers - page 4
31
If the frequency of the tuning fork at resonance is 256Hz, calculate the frequency of vibration of the wire when the tension in he wire is increased to 196N
A
130.6Hz
B
182.9Hz
C
358.4Hz
D
501.8Hz
correct option: c
\(\frac{f}{256} = \sqrt{\frac{196}{100}}\)
f = \(\sqrt{\frac{256^2 \times 196}{100}}\)
= 356.4Hz
Users' Answers & Commentsf = \(\sqrt{\frac{256^2 \times 196}{100}}\)
= 356.4Hz
32
The magnitude of the gravitational force between two particles 0.10m apart is 10N. If the distance between them is increased to 0.20m, calculate the magnitude of the new force
A
40.0N
B
20.0N
C
5.0N
D
2.5N
correct option: d
\(g_1 = \frac{Gm_1m_2}{r^2_1}\)
\(m_1m_2 = \frac{gr^2_1}{G}\)
\(g_2 = \frac{Ggr^2_1}{Gr^2_2} = \frac{10 \times 0.1^2}{0.2^2}\)
= 2.5N
Users' Answers & Comments\(m_1m_2 = \frac{gr^2_1}{G}\)
\(g_2 = \frac{Ggr^2_1}{Gr^2_2} = \frac{10 \times 0.1^2}{0.2^2}\)
= 2.5N
33
As the plates of a charged variable capacitor are moved closer together, the potential difference between them
A
increased
B
decrease
C
remains the same
D
is doubled
correct option: b
Users' Answers & Comments34
What is the effective capacitance in the circuit?
A
2\(\mu F\)
B
6\(\mu F\)
C
18\(\mu F\)
D
216\(\mu F\)
correct option: a
\(\frac{1}{c} = \frac{1}{6} + \frac{1}{6} + \frac{1}{6}\)
= \(\frac{1 + 1 + 1}{6} = \frac{3}{6} = \frac{1}{2}\)
= 2\(\mu F\)
Users' Answers & Comments= \(\frac{1 + 1 + 1}{6} = \frac{3}{6} = \frac{1}{2}\)
= 2\(\mu F\)
35
What is the total energy stored by the capacitors?
A
2.0 x 10-4J
B
1.0 x 10-4J
C
9.0 x 10-2J
D
1.0 x 10-2J
correct option: d
Energy = \(\frac{1}{2}CV^2 = \frac{1}{2} \times 2 \times 10^{-6} \times 100^2\)
= 1.0 x 10-2J
Users' Answers & Comments= 1.0 x 10-2J
36
Three identical lamps each power 100W are connected in parallel across a potential difference of 250V. Calculate the current in the circuit
A
7.5A
B
2.5A
C
1.2A
D
0.8A
correct option: c
P = IV
I = \(\frac{P}{V} = \frac{3 \times 100}{250} = 1.2A\)
Users' Answers & CommentsI = \(\frac{P}{V} = \frac{3 \times 100}{250} = 1.2A\)
37
An electric bulb is rated 60W, 220V. Calculate the resistance of its filament when it is operating normally
A
296.7\(\Omega\)
B
400.0\(\Omega\)
C
512.2\(\Omega\)
D
806.7\(\Omega\)
38
The Earth's magnetic equator passes through Jos in Nigeria. At Jos. the
A
angle of variation is zero
B
magnetic declination is 90o
C
angle of dip is zero
D
horizontal component of the Earth's magnetic field is zero
correct option: c
Users' Answers & Comments39
Which of the following statements about magnetic lines of force is not correct?
A
a magnnetic line of force is an imaginary line which the north pole of a magnet would describe if it is free to moves
B
magnetic lines of force do not cross one another
C
magnetic lines of force are closely packed together at neutral point
D
the presence of magnetic lines of force in a region indicates the presence of a magnetic field
correct option: c
Users' Answers & Comments40
The material used for constructing the core of an electromagnet is
A
iron
B
carbon
C
copper
D
steel
correct option: a
Users' Answers & Comments