2002 - WAEC Physics Past Questions and Answers - page 5
41
A transformer has 400 turns and 200 turns in the primary and secondary windings respectively. If the current in the primary and secondary windings are 3A and 5A respectively. calculate the efficiency of the transformer?
A
85.0%
B
83.3%
C
37.5%
D
30.0%
correct option: b
Users' Answers & Comments42
A freely-suspended magnet swinging in a horizontal plane comes to rest with its axis pointing approximately
A
north-south
B
south-west
C
north-east
D
south-east
correct option: a
Users' Answers & Comments43
Calculate the inductance L, of the coil in the circuit diagram shown above
A
3.8H
B
0.6H
C
0.4H
D
0.2H
correct option: b
XL = \(\frac{V}{I} = \frac{240}{2} = 120\Omega\)
L = \(\frac{X_L}{2 \pi f}\)
= \(\frac{120 \times \pi}{2 \times \pi \times 100}\)
= 0.6H
44
In a model of the hydrogen atom, the energy levels Wn are given by the formula Wn = -\(\frac{R}{n^2}\), where n is an integer and R is a constant. Determine the energy released in the transition from n = 3 to n = 2.
A
\(\frac{R}{5}\)
B
-\(\frac{R}{4}\)
C
\(\frac{5R}{36}\)
D
\(\frac{-5R}{36}\)
correct option: b
Users' Answers & Comments45
If a radioactive atom emits a beta particle, Its mass number
A
increases by one
B
remains the same
C
decreases by one
D
increases by two
correct option: b
Users' Answers & Comments46
Which of the following is usually used to cause fission in an atomic reactor?
A
Alpha particles
B
beta particles
C
electrons
D
Neutrons
correct option: d
Users' Answers & Comments47
Which of the following materials is used to control the rate of neutron production in a nuclear reactor?
A
boron rods
B
concrete shield
C
graphite rods
D
uranium rods
correct option: a
Users' Answers & Comments48
A nuclide X is produced by bombarding a nitrogen(N) nucleus with an alpha(\alpha\) particle with the release of heavy hydrogen(D) nucleus as shown by the following nuclear equation, \(\alpha + ^{14}_{7}N \to ^p_qX + ^2_1D\). Determine the values of p and q in the equation
A
12 and 6
B
14 and 7
C
16 and 8
D
19 and 8
correct option: c
Users' Answers & Comments