2013 - WAEC Physics Past Questions and Answers - page 4
31
a charge of 2.0 x 10-5C experiences a force of 80N in a uniform electric field. Calculate the magnitude of the electric field intensity
A
8.0 x 106 NC-1
B
4.0 x 106 NC-1
C
4.0 x 104 NC-1
D
2.0 x 104 NC-1
correct option: b
E = \(\frac{F}{Q} = \frac{80}{2 \times 10^{-5}}\)
= 4 x 106 NC-1
Users' Answers & Comments= 4 x 106 NC-1
32
A potential difference of 12V is applied across the ends of a 6\(\Omega\) resistor for 10 minutes. Determine the quantity of heat generated
A
720J
B
1200J
C
14400J
D
43200J
correct option: c
Q = \(\frac{V^2 t}{R} = \frac{12^2 \times 10 \times 60}{6}\)
= 14400J
Users' Answers & Comments= 14400J
33
Which of the following instruments is used to determine the accurate value of the electromotive force of a cell?
A
voltmeter
B
meterbridge
C
voltameter
D
potentiometer
correct option: d
Users' Answers & Comments34
The capacitance of parallel plates capacitors varies
A
inversely as the square of the distance between the plates
B
directly as the square of the distance between the plates
C
inversely as the distance between the plates
D
directly as the distance between the plate
correct option: a
Users' Answers & Comments35
Which of the following devices does not makes use of eddy current for its action? A/An
A
galvanometer
B
speedometer
C
induction furnace
D
speedometer
correct option: a
Users' Answers & Comments36
A coil of inductance 0.12 H and resistance 4\(\Omega\), is connected across a 240V, 50Hz supply. Calculate the current through it. [\(\pi\) = 3.142]
A
6.3A
B
33.3A
C
37.2A
D
40.0A
correct option: a
XL = \(2\pi f L\)
= = 2 x 3.142 x 50 x 0.12
= 37.68\(\Omega\)
Z = \(\sqrt{R^2 + X_L^2} = \sqrt{4^2 + 37.68^2}\)
I = \(\frac{V}{z} = \frac{240}{37.89}\)
= 6.3A
Users' Answers & Comments= = 2 x 3.142 x 50 x 0.12
= 37.68\(\Omega\)
Z = \(\sqrt{R^2 + X_L^2} = \sqrt{4^2 + 37.68^2}\)
I = \(\frac{V}{z} = \frac{240}{37.89}\)
= 6.3A
37
The work function of a metal is 2.56 x 10-19J. Calculate the frequency of a photon whose energy is required to eject from the metal an electron with kinetic energy of 3.0ev. [1 eV = 1.6 x 10-19J, h = 6.6 x 10-34Js]
A
5.56 x 1019Hz
B
1.66 x 1019Hz
C
1.12 x 1015Hz
D
8.42 x 1014Hz
correct option: c
F = \(\frac{K.E + Wo}{h}\)
= \(\frac{3.0 \times 1.6 \times 10^{-19} + 2.56 \times 106{-19}}{6.6 \times 106{-34}}\)
- 1.12 x 10-15HZ
Users' Answers & Comments= \(\frac{3.0 \times 1.6 \times 10^{-19} + 2.56 \times 106{-19}}{6.6 \times 106{-34}}\)
- 1.12 x 10-15HZ
38
The minimum energy required to cause photoelectric emission when the surface of a metal is irradiated with electromagnetic radiation of suitable frequency is called
A
critical energy
B
ionization energy
C
work function
D
planck's constant
correct option: c
Users' Answers & Comments39
Which of the following particles are termed nucleons in a neutral atom?
A
protons and neutrons
B
neutrons and electrons
C
protons and electrons
D
protons, electrons and neutrons
correct option: a
Users' Answers & Comments40
Which of the following statements about the use of radioisotopes is not correct? They are used to
A
induce mutations in plants and animals to obtain new and improved varieties
B
trace the paths of metabolic processes in plants and animals
C
estmate the age of rocks
D
locate broken bones
correct option: a
Users' Answers & Comments