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Physics
UTME / JAMB 2019
Waves, Sound & Vibrations
Solution
Which of the following equations is the correct definition of the reactance of an indicator L?
A
Reactance = (Amplitude of voltage) \(\div\) (Amplitude of current)
B
Reactance = (Amplitude of voltage) x (Amplitude of current)
C
Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)
D
Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)\(\frac{1}{2}\)
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Reactance is the value of an indicator or a capacitor in ohms
Source: Myschool Past Questions Archive (Record #54995)
Physics
UTME / JAMB 2019
Atomic, Quantum, Nuclear Physics & Electronics
Solution
Ripple in a power supply unit is caused by
A
using an alternating current source
B
forward voltage drop
C
heavy load
D
using a zener diode
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
The fluctuation of d.c signal results from the rectification of A.C source to d.c.
Source: Myschool Past Questions Archive (Record #54997)
Physics
UTME / JAMB 2019
Elasticity, Density, Pressure & Fluids
Solution
When the temperature of a liquid is increased, its surface tension?
A
increases
B
decreases
C
remain constant
D
increases then decreases
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
Surface tension or elasticity of a fluid decreases with increased temperature
Source: Myschool Past Questions Archive (Record #55000)
Physics
UTME / JAMB 2019
Lenses & Optical Instruments
Solution
The distance between an object and its real image in a convex lens is 40cm. If the magnification of the image is 3, calculate the focal length of the lens
A
6.5 cm
B
7.5 cm
C
8.5 cm
D
4.5 cm
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
u + v = 40
\(\frac{v}{u}\) = 3
v = 3u
u + 3u = 40
4u = 40
u = 10cm
v = 3u = 30cm
f = \(\frac{uv}{u + v} = \frac{10(30)}{10 + 30} = \frac{300}{40}\)
= 7.5 cm
Source: Myschool Past Questions Archive (Record #55005)
Physics
UTME / JAMB 2019
Reflection, Refraction & Dispersion of Light
Solution
A ray of light passes through the centre of curvature of a concave mirror and strikes the mirror. At what angle is the ray reflected?
A
180\(^o\)
B
90\(^o\)
C
0\(^o\)
D
60\(^o\)
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
- a ray of light passing through the centre of a curvature is returned along the same path
- angle difference along the same path is zero
Source: Myschool Past Questions Archive (Record #55008)
Physics
UTME / JAMB 2019
Current Electricity & Electric Circuits
Solution
The pin-hole camera produces a less sharply defined image when the
A
pin-hole is larger
B
illumination is less
C
screen is further from the pin-hole
D
object is further from the pin-hole
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
- a less sharp or blurred image is due to increased brightness
- increase brightness is also due to large hole or many pin holes
Source: Myschool Past Questions Archive (Record #55010)
Physics
UTME / JAMB 2019
Current Electricity & Electric Circuits
Solution
A straight wire 15cm long, carrying a current of 6.0A is in a uniform field of 0.40T. What is the force on the wire when it is at right angle to the field
A
0.46N
B
0.35N
C
0.36N
D
0,24N
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
F = BIL = 0.4 x 6 x \(\frac{15}{100}\)
= 0.36N
Source: Myschool Past Questions Archive (Record #55012)
Physics
UTME / JAMB 2019
Work, Energy, Power & Simple Machines
Solution
The pitch of a screw jack is 0.45cm and the arm is 60cm long. If the efficiency of the Jack is 75/\pi %, calculate the mechanical advantage.
A
400
B
300
C
200
D
150
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
P = 0.45cm, L = 60cm, Eff = 75/\pi%
VR
(Screw
system)
=
2\pir
P
=
2\piL
P
M.A
=
Eff% \times VR
100
=
75
\pi
\times
1
100
\times
2\pi \times 60
0.45
=
75 \times 800
300
=
200
Source: Myschool Past Questions Archive (Record #55044)
Physics
UTME / JAMB 2019
Magnetism, Electromagnetism & AC Circuits
Solution
When the downward current flows in a straight vertical conductor, the direction of its magnetic field at a point due north of the wire is?
A
Upward
B
North
C
South
D
West
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
At a point due N of the wire, the field is due west, at a point due S of the wire, the field is due eest.
Source: Myschool Past Questions Archive (Record #55058)
Physics
UTME / JAMB 2019
Electrostatics & Capacitors
Solution
Aluminium is sometimes used as the leaf of an electroscope because it
A
is a light material
B
is a good conductor
C
is a good insulator
D
can be converted into thin sheets
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
- Aluminium can be made in thin sheet like Gold.
- the leaf is a thin material that can be diverged easily.
Source: Myschool Past Questions Archive (Record #55061)
Physics
UTME / JAMB 2019
Elasticity, Density, Pressure & Fluids
Solution
The diagram above represents the stress-strain graph of a loaded wire. Which of these statements is correct?
A
At J, the wire becomes plastic
B
J is the yield point
C
L is the elastic limit
D
At K, the wire breaks
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
- I is the elastic limit
- the end of the constant part J is the yield point
- L is the break point.
Source: Myschool Past Questions Archive (Record #55067)
Physics
UTME / JAMB 2019
Electrostatics & Capacitors
Solution
A supply of 400V is connected across capacitors of 3\muf and 6\muf in series. Calculate the charge
A
8 x 10\(^{-4}\)C
B
4 x 10\(^{-2}\)C
C
8 x 10\(^{-3}\)C
D
4 x 10\(^{-8}\)C
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
C\(_T\) = \(\frac{C_1 \times C_2}{C_1 + C_2}\)
= \(\frac{3 \times 6}{3 + 6}\)
= \(\frac{18}{9}\) = 2\muf
Q = CV
⇒ 2 \times 10\(^{-6}\) \times 400
⇒ 800 \times 10\(^{-6}\)C = 8 \times 10\(^{-4}\)C
Source: Myschool Past Questions Archive (Record #55090)
Physics
UTME / JAMB 2019
Waves, Sound & Vibrations
Solution
A vibrator causes water ripples to travel across the surface of a tank. The wave travels 50cm in 2s and the distance between successive crests is 5cm. Calculate the frequency of the vibrator
A
5Hz
B
6Hz
C
5.2Hz
D
25Hz
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
\(V = \frac{Distance}{time}\)
= \(\frac{50cm}{2s}\)
= 25 cms\(^{-1}\).
\(V = f \lambda\)
\(f = \frac{V}{\lambda}\)
\(f = \frac{25}{5}\)
= 5 Hz
Source: Myschool Past Questions Archive (Record #55098)
Physics
UTME / JAMB 2019
Temperature, Thermometry & Thermal Expansion
Solution
A thermocouple thermometer is connected to a millivoltmeter which can read up to 10mV. When one junction is in ice at 0^\circC and the other is steam at 100^\circC, the millivoltmeter reads 4mV. What is the maximum temperature which this arrangement can measure
A
100\(^o\)C
B
248\(^o\)C
C
250\(^o\)C
D
350\(^o\)C
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
t\(_\theta\) - t\(_o\) = 10,
t\(_{100}\) - t\(_o\) = 4
\theta
=
t\(_\theta\) - t\(_o\)
t\(_{100}\) - t\(_o\)
\times
100
10
4
\times
100
=
250^\circC
Source: Myschool Past Questions Archive (Record #55103)
Physics
UTME / JAMB 2019
Magnetism, Electromagnetism & AC Circuits
Solution
An alternating current can induce voltage because it has
A
ripple value
B
varying magnetic field
C
weaker magnetic field than direct current
D
high peak value
medium Difficulty
Verified Correct Answer: Option B
Physical Principles & Numerical Solution
As induced voltage is produced by varying magnetic field. The induced voltage is proportional to the rate of change of magnetic flux linking the coil.
Source: Myschool Past Questions Archive (Record #55227)