2009 - WAEC Physics Past Questions and Answers - page 5
41
An inductor of inductance 1.0H is connected in series with a capacitor of capacitance 2.0\(\mu F\) in an a.c. circuit. to resonate
A
112.5Hz
B
225.0Hz
C
323.5Hz
D
707.1Hz
correct option: a
fo = \(\frac{1}{2 \pi \sqrt{LC}} = \frac{1}{2 \times 3.14 \sqrt{1 \times 2 \times 10^{-6}}}\)
= 112.5Hz
Users' Answers & Comments= 112.5Hz
42
An ammeter connected to an a.c circuit records 5.5. The peak current in the circuit is
A
7.8A
B
7.1A
C
3.8A
D
3.5A
correct option: a
\(I_o = I_{rms} \times \sqrt{2} = 5.5 \times 1.41 = 7.8A\)
Users' Answers & Comments43
Two isotopes of uranium are designed as \(^{238}U\) and \(^{235}U\). The numbers 238 and 235 represent their
A
atomic numbers
B
nucleon numbers
C
proton numbers
D
neutron numbers
correct option: b
neutrons + protons = the nucleus or mass numbers.
U-238 has mass number(proton 92 + neutron 146=238)
U-235 has mass number (proton 92 + neutron 143 =235)
Users' Answers & CommentsU-238 has mass number(proton 92 + neutron 146=238)
U-235 has mass number (proton 92 + neutron 143 =235)
44
The main difference between between x-rays and \(\gamma-rays\) lies in their
A
ionizing ability
B
absorption rate
C
mode of production
D
mode of propagation
correct option: d
Users' Answers & Comments45
An electron of mass 9.1 x 10-31 kg moves with a speed of 107ms-1. Calculate the wavelength of the associates wave[h = 6.6 x 10-34Js]
A
9.0 x 10-24m
B
4.55 x 10-17m
C
7.25 x 10-11m
D
6.20 x 10-8m
correct option: c
\(\lambda = \frac{hc}{\frac{1}{2}mv^2}\)
= \(\frac{6.6 x 10^{-34} \times 3 \times 10^8}{0.5 \times 9.1 \times 10^{-3} (10^7)^2}\)
= 7.25 x 10-11m
Users' Answers & Comments= \(\frac{6.6 x 10^{-34} \times 3 \times 10^8}{0.5 \times 9.1 \times 10^{-3} (10^7)^2}\)
= 7.25 x 10-11m