1997 - WAEC Physics Past Questions and Answers - page 5
41
The current in a series R-L-C circuit attains its maximum value when the
A
Impedance is greater than the capacitive reactance
B
Inductive reactance is equal to the capacitive reactance
C
Inductive reactance is greater than the capacitive reactance
D
capacitive reactance is less than resistance
correct option: b
Users' Answers & Comments42
A charge of 1 x \(10^{-5}\)C experiences a force of 40N at a certain point in space. What is the magnitude of the electric field intensity at the point in Newton and couloumb
A
8 x \(10^{6}\)
B
4 x \(10^{6}\)
C
3 x \(10^{-4}\)
D
2 x \(10^{-4}\)
correct option: b
\(E= \frac{F}{O}= \frac{40}{1\times10^{-5}}=4 \times10^{6}\)
Users' Answers & Comments43
A capacitor of capacitance 25µF is connected to an a.c power source of frequency 200/πHz. Calculate the reactance of the capacitor
A
0.01Ω
B
0.02Ω
C
50Ω
D
100Ω
correct option: d
\(X_c=\frac{1}{2\pi{fc}}\)=\(\frac{1}{2\times\pi\times\frac{200}{\pi}\times 25\times 10^{-6}}=\frac{10^6}{10^4}\)=100 Ω
Users' Answers & Comments44
During the electrolysis of copper (II) tetraoxosulphate (VI) solution, an ammeter shows a steady reading of 1A for 30minutes while 6.6 x \(10^{-4}\)kg of copper is liberated. Calculate the error in the ammeter The electrochemical equivalent of copper is 3.30 x \(10^{-7}kgC{-1}\)
A
0.001A
B
0.011A
C
0.111A
D
1A
correct option: c
m=zIt, \(I=\frac{m}{zt}= \frac{6.6\times10^{-4}}{3.3 \times10^{-7}\times 1800}=1.1111\ \)error=1.1111-1.0=0.111A.
Users' Answers & Comments45
In a nuclear reaction, the mass defect is 2 x \(10^{-6}\)g. Calculate the energy released given that the velocity of light is 3 x \(10^{8}ms^{-1}\)
A
9 x \(10^{7}\)J
B
1.8 x \(10^{8}\)J
C
1.8 x \(10^{9}\)J
D
9 x \(10^{-10}\)J
correct option: b
E=\(mc^2 = 2\times10^{-6} \times10^{-3}\times(3\times10^{8})^2=1.8\times10^{8}\)
Users' Answers & Comments46
An atom radiates 1.5 x \(10^{-19}\)J of energy when an electron jumps from one energy level to another. What is the wavelength of the emitted radiation? (Planck’s constant =6.6 x \(10^{-34}\)Js. Speed of light in air=3 x \(10^{8}ms^{-1}\)
A
1.32 x \(10^{-6}\)m
B
2.98 x \(10^{-6}\)m
C
3.32 x \(10^{-6}\)m
D
6.82 x \(10^{-6}\)m
correct option: a
\(E=\lambda v=\frac{hc}{\lambda}\Rightarrow\lambda=\frac{hc}{E}={6.6 \times10^{-34}\times3\times10^8}{1.5\times10^{-19}}\=1.32\times10^{-6}\)
Users' Answers & Comments