2012 - WAEC Physics Past Questions and Answers - page 5
41
An inductor is connected to a 24V, 50Hz mains supply. If the current through the inductor is 1.5A, calculate the inductance of the inductor (\(\pi = \frac{22}{7}\))
A
8.0 x 102H
B
7.5 x 10oH
C
1.6 x 10oH
D
5.1 x 10-2H
correct option: d
\(X_L = \frac{V}{I} = \frac{24}{1.5} = 16\Omega\)
L = \(\frac{XL}{2 \pi f} = \frac{16}{2 \pi 50}\)
= 0.05H
Users' Answers & CommentsL = \(\frac{XL}{2 \pi f} = \frac{16}{2 \pi 50}\)
= 0.05H
42
In a R-C circuit
A
Irms leads Vrms by 60o
B
Irms slags Vrms by 60o
C
Vrms lags Irms by 90o
D
Vrms leads Irms by 90o
correct option: c
Users' Answers & Comments43
An atom in an excited state is one whose
A
potential energy is minimum
B
potential energy is maximum
C
electron are in the conduction band
D
electron have moved to higher energy level
correct option: d
Users' Answers & Comments44
A metal with a work function of 3.0ev is irradiated with ultraviolet light of energy 4.0 ev. The kinetic energy of the ejected electron is
A
1.0eV
B
3.0eV
C
4.0eV
D
7.0eV
45
Which of the following statements about X-rays is correct? X-rays
A
are produced when a metal surface is irradiated with ultraviolet light
B
are produced when a metal target is used to block fast miving electrons
C
have long wavelengths and are therefoer very penetrating
D
are not part of the electromagnetic spectrum
correct option: b
Users' Answers & Comments46
Which of the following arrangements of radiations is in the order of decreasing penetrating power?
A
\(\alpha, \beta, \gamma\)
B
\(\alpha, \gamma, \beta\)
C
\(\gamma, \beta, \alpha\)
D
\(\beta, \gamma, \alpha\)
47
Which of the following radiations emitted in radioactive decay has momentum, a fairly high penetrating power and is deflected by a magnet?
A
alpha particles
B
beta particle
C
gamma radiation `
D
X-radiation
correct option: b
Users' Answers & Comments