JAMB UTME - Physics - 2019
Question 1 Report
Neutrons were discovered by
Answer Details
Neutrons were discovered by James Chadwick. In 1932, he conducted an experiment in which he bombarded a thin sheet of beryllium with alpha particles. He observed that a new type of radiation was emitted that was not affected by electric or magnetic fields. He concluded that this radiation was composed of particles that were neutral and had a mass similar to that of a proton. He called these particles "neutrons," and his discovery revolutionized our understanding of atomic structure and led to the development of nuclear energy.
Question 2 Report
When water is boiling, it
Answer Details
When water is boiling, it changes from a liquid state to a gaseous state called steam. This happens when the water is heated to its boiling point, which is when it reaches a temperature of 100 degrees Celsius (212 degrees Fahrenheit) at sea level. As the water is heated, it absorbs energy and the molecules start to move faster and faster, eventually reaching a point where they escape into the air as steam. The temperature of the water during boiling does not change, as all the energy is being used to break the bonds between the water molecules rather than increasing the temperature. Therefore, the options "gets hotter," "increase in mass," and "decreases in mass" are not correct when describing what happens when water is boiling.
Question 3 Report
The lower fixed part of a faulty thermometer reads 2°C while the upper fixed point is 100°C.
What is the true temperature when the thermometer reads 51°C?
Answer Details
Since the thermometer is faulty, it is not measuring the temperature accurately. To find the true temperature, we need to determine the extent of the error in the thermometer. We can do this by comparing the difference between the lower fixed point and the reading with the difference between the upper fixed point and the true temperature. Since the lower fixed point reads 2°C and the upper fixed point reads 100°C, and the thermometer reading is 51°C, we can calculate the error as follows: True temperature = (51°C - 2°C) / (51°C - 2°C) * (100°C - 51°C) + 51°C = 50°C So, the true temperature when the thermometer reads 51°C is 50°C, which is option B.
Question 4 Report
A cone is in unstable equilibrium has its potential energy
Answer Details
In unstable equilibrium, potential energy decreases as the height decreases.
Question 5 Report
A train has an initial velocity of 44m/s and an acceleration of -4m/s\(^{2}\). Calculate its velocity after 10 seconds
Answer Details
The velocity of the train after 10 seconds can be calculated using the formula: v = u + at where v is the final velocity, u is the initial velocity, a is the acceleration, and t is the time. Substituting the given values, we get: v = 44 m/s + (-4 m/s^2) x 10 s v = 44 m/s - 40 m/s v = 4 m/s Therefore, the velocity of the train after 10 seconds is 4m/s. Answer option D is correct. Explanation: The train has an initial velocity of 44 m/s and an acceleration of -4 m/s^2. The negative sign indicates that the acceleration is in the opposite direction to the initial velocity, which means that the train is slowing down. After 10 seconds, the train's velocity decreases by 40 m/s (4 m/s^2 x 10 s) to reach a final velocity of 4 m/s.
Question 6 Report
The conductivity of gases at low pressure can be termed as
I. hot cathode emission
II. thermo ionic emission
III. cold cathode emission
IV. Field emission
Answer Details
As conduction of gases is at low pressure and high voltage, called field or cold cathode emission.
Question 7 Report
A coil X is moved quickly away from the end Y of a stationary metal bar and a current then flows in X as shown above.
Then
Answer Details
N - S magnet is moved towards a coil production clockwise direction of current in the coil.
- This is the same as a coil moved away from S-N (Y - North pole)
Question 8 Report
Calculate the velocity ratio of a screw jack of pitch 0.2cm if the length of the tommy bar is 23cm
Answer Details
P = 0.2cm, L = r = 23cm
| VR | = | 2?rP | = | 2?LP | = | 2?×230.2 | = | 230? |
Question 9 Report
Which of the following bodies, each with centre of gravity G, lying on a horizontal table, is/are in unstable equilibrium?
Answer Details
- I and II are in neutral equilibrium. They will roll continuously on the table
- III is a body with high centre of gravity (unstable)
- IV is a body with high centre of gravity (stable)
Question 10 Report
Which of the following is consistent with Charles' law?
I
II 
III
IV. 
Answer Details
This is the correct graph. The graph is volume against 1/ temperature where temperature is in Celsius.
Question 11 Report
The limiting frictional force between two surface depends on
I. the normal reaction between the surfaces
II. the area of surface in contact
III. the relative velocity between the surfaces
IV. the nature of the surface
Answer Details
The correct answer is "I and IV only". The limiting frictional force between two surfaces depends on the normal reaction between the surfaces (I) and the nature of the surface (IV). The normal reaction is the force that the surfaces exert on each other perpendicular to the plane of contact. The greater the normal reaction, the greater the frictional force that can be applied before motion occurs. The nature of the surface is determined by factors such as roughness, hardness, and texture, which can affect the frictional force. The area of surface in contact (II) does not directly affect the limiting frictional force, although it can affect the force required to initiate motion. For example, if the area of contact is small, the pressure between the surfaces will be higher, making it harder to initiate motion. The relative velocity between the surfaces (III) also does not directly affect the limiting frictional force, although it can affect the force required to maintain motion. If the surfaces are already in motion, a lower force may be required to keep them moving than to initiate motion. In summary, the limiting frictional force between two surfaces depends primarily on the normal reaction and the nature of the surface, and is not directly affected by the area of contact or the relative velocity between the surfaces.
Question 12 Report
Workdone on an object to bring it to a certain point in space is called
Answer Details
The work done on an object to bring it to a certain point in space is called "Potential Energy". Potential energy is a form of energy that an object possesses due to its position relative to other objects. When an object is lifted or moved to a higher point against gravity, work is done on it, and this work is stored as potential energy. The potential energy of an object is directly proportional to its height and mass. It can be converted into other forms of energy, such as kinetic energy, when the object is released or allowed to move freely. Therefore, potential energy is a type of stored energy that an object has due to its position, and it can be released to do work.
Question 13 Report
A thermocouple thermometer is connected to a millivoltmeter which can read up to 10mV. When one junction is in ice at 0°C and the other is steam at 100°C, the millivoltmeter reads 4mV. What is the maximum temperature which this arrangement can measure
Answer Details
The maximum temperature which this arrangement can measure is 250°C. A thermocouple thermometer works by using the thermoelectric effect, which is the phenomenon that occurs when two dissimilar metals are joined together to form a loop and a temperature difference is established between the two junctions. This temperature difference generates a small electrical voltage, which can be measured using a millivoltmeter. The voltage generated is proportional to the temperature difference between the two junctions. In the case of the thermocouple thermometer described, one junction is in ice at 0°C and the other is steam at 100°C, and the millivoltmeter reads 4mV. This means that the voltage generated by the thermocouple is 4 millivolts, which corresponds to a temperature difference of 100°C. However, the millivoltmeter can only read up to 10mV, so the maximum temperature difference it can measure is 10mV / 4mV/°C = 250°C. This means that the maximum temperature which this arrangement can measure is 250°C.
Question 14 Report
A metal rod has a length of 100cm at \(200^\circ C\). At what temperature will its length be 99.4cm. If the linear expansivity of the material of the rod is \(2 \times 10^{-5}C^{-1}\)
Answer Details
The linear expansivity of a material describes how its length changes with temperature. If the linear expansivity is given as 2 × 10^-5/°C, this means that for every 1°C change in temperature, the length of the material will change by 2 × 10^-5 times its original length. Given that the rod has a length of 100 cm at 200°C, we can use this information to find its length at a different temperature. If we let L be the length of the rod at temperature T, we can write the relationship as follows: L = 100 cm * (1 + 2 × 10^-5 * (T - 200°C)) To find the temperature at which the rod will have a length of 99.4 cm, we can set L equal to 99.4 cm and solve for T: 99.4 cm = 100 cm * (1 + 2 × 10^-5 * (T - 200°C)) 99.4 cm / 100 cm = 1 + 2 × 10^-5 * (T - 200°C) 0.994 = 1 + 2 × 10^-5 * (T - 200°C) -0.006 = 2 × 10^-5 * (T - 200°C) -0.006 / 2 × 10^-5 = T - 200°C -0.006 / (2 × 10^-5) = T - 200°C -0.006 / (2 × 10^-5) + 200°C = T So the temperature at which the rod will have a length of 99.4 cm is approximately equal to -0.006 / (2 × 10^-5) + 200°C, or -100°C. Therefore, the answer is -100°C.
Question 15 Report
If a body moves with a constant speed and at the same time undergoes an acceleration, its motion is said to be
Answer Details
If a body moves with a constant speed but at the same time undergoes an acceleration, its motion is called rectilinear motion. This means that the body moves in a straight line and its speed changes at a constant rate, causing an acceleration. It is different from oscillation, circular and rotational motions which involve changes in direction, as well as changes in speed.
Question 16 Report
If the attraction of the sun is suddenly ceased, the earth would continue to move in a straight line making a tangent with the original orbit. This statement is derived from Neutron's
Answer Details
The correct answer is the First law of motion. The First law of motion, also known as the law of inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. In this case, the earth is moving in its orbit around the sun because of the force of gravity between the two objects. If the force of gravity suddenly ceased, the earth would no longer be acted upon by an external force and would continue to move in a straight line, making a tangent with its original orbit. This idea is attributed to Sir Isaac Newton, who developed the laws of motion and the law of universal gravitation. However, the specific statement mentioned in the question is derived from the First law of motion.
Question 17 Report
When the temperature of a liquid is increased, its surface tension
Answer Details
Surface tension or elasticity of a fluid decreases with increased in temperature
Question 18 Report
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?
Answer Details
When a light ray passes through the center of curvature of a concave mirror and strikes the mirror, the reflected ray will be reflected back on itself, creating an angle of 0 degrees. Therefore, the correct answer is 0o.
Question 19 Report
A supply of 400V is connected across capacitors of 3μf and 6μf in series. Calculate the charge
Answer Details
| CT | = | C1 × C2 C1 + C2 |
| = | 3 × 63 + 6 |
= 189
= 2μf
Q = CV
⇒ 2 × 10−6
× 400
⇒ 800 × 10−6
C = 8 × 10−4
C
Question 20 Report
Any line or section taken through an advancing wave in which all the particles are in the same phase is called the
Answer Details
The answer is: wave front. A wave front is any imaginary line or surface that connects all points of a wave that are in the same phase, meaning they are at the same point in their cycle. In other words, it is a line or surface that separates the points of a wave that are in-phase from those that are out-of-phase. For example, consider the ripples on the surface of a pond when a stone is thrown in. The wave fronts are the concentric circles that emanate from the point where the stone entered the water. All points along a given circle are in-phase, meaning the water molecules at those points are at the same point in their oscillation cycle. In summary, a wave front is a line or surface that separates points in a wave that are in-phase from those that are out-of-phase.
Question 21 Report
Gases conduct electricity under
Answer Details
Gases conduct electricity under low pressure and high voltage
Question 22 Report
A body moves in SHM between two point 20m on the straight line Joining the points. If the angular speed of the body is 5 rad/s. Calculate its speed when it is 6m from the center of the motion.
Answer Details
From two parts 20m apart
a = 10m, x = 6m, A = 5
V = ω√A2−X2
= 5√102−62
= 40m/s
Question 23 Report
The lead-acid accumulator consists of
Answer Details
- the positive pole is lead peroxide (PbO2
)
- the negative pole is head
- the electrolyte is H2
SO4
Question 24 Report
Which of the following is/are the limitations to the Rutherford's atomic models?
I. It is applicable when energy is radiated as electrons are revolving
II. It is applicable when energy is radiated in a continuous mode
III. It is applicable to an atom with only one electron in the other shell
Answer Details
Rutherford assumed that (I) energy is radiated when electrons are revolving (II) energy is radiated in a continuous mode. These are limitations of Rutherford's model
Question 25 Report
According to kinetic molecular model, in gases
Answer Details
According to the kinetic molecular model, in gases, the molecules are very fast apart and occupy all the space made available. This means that gas molecules are in constant random motion and they move freely in all directions without any regular arrangement. They collide with each other and with the walls of the container, exerting pressure. The temperature of the gas is related to the average kinetic energy of the gas molecules. The higher the temperature, the faster the gas molecules move, and the higher the kinetic energy.
Question 26 Report
The angular dispersion of a prism depends on
Answer Details
Dispersion is due to different refractive indices speeds and wavelengths.
Question 27 Report
A man on a bench will exert the greatest pressure on the bench when he
Answer Details
The man on the bench will exert the greatest pressure when he stands on the toes of one foot. This is because when he stands on one foot, all his weight is concentrated on a smaller surface area of the bench, resulting in more pressure. The pressure he exerts is calculated by dividing his weight by the surface area in contact with the bench. When he stands on one foot, the surface area is smaller, which means the pressure exerted is greater. In comparison, when he lies flat on his back or belly, or when he stands on both feet, his weight is distributed over a larger surface area, resulting in less pressure.
Question 28 Report
Which of these is observed when air is pumped out of a discharge tube without lowering its pressure
Answer Details
Conduction takes places in gases when air is pumped out of a discharged tube under reduced pressure.
Question 29 Report
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
Answer Details
At a point due N of the wire, the field is due east, at a point due S of the wire, the field is due west.
Question 30 Report
Which of the following statements are correct of the production and propagation of waves?
I. vibration produces waves
II. waves transmit energy along the medium
III. the medium through which the wave travels does not travel with the wave
IV. waves do not require any medium for transmission
Answer Details
The correct statement is: I and II and III only. Explanation: - Statement I is correct because the production of waves involves some kind of disturbance that creates a vibration in the medium, which then propagates as a wave. - Statement II is correct because waves carry energy along the medium as they propagate. This is why waves can be used to transmit information or power over long distances. - Statement III is correct because the medium through which a wave travels does not move with the wave. Instead, the wave passes through the medium, causing it to oscillate or vibrate, but not to move along with the wave. - Statement IV is incorrect because most waves require a medium through which to propagate. For example, sound waves require air, water waves require water, and seismic waves require the Earth's crust. There are some types of waves, such as electromagnetic waves, that can propagate through a vacuum, but this is not true for all waves.
Question 31 Report
The height at which the atmosphere cases to exist is about 80km. If the atmospheric pressure on the ground level is 760mmHg, the pressure at a height of 20km above the ground level is
\((\rho_m = 13.6g/cm^3\ \rho = 0.00013g/cm^3)\)
Answer Details
ρm
hm
= ρa
ha
13.68(760 - p) × 10−3
= 13 × 10−5
(20 × 103
)
| 760 | - | p | = | 13 × 10−5 × 20 × 103 13.68 × 10−3 | = | 19.00 | × | 101 |
760 - p = 190
p = 760 - 190 = 570mmHg
Question 32 Report
The earth's gravitational field intensity at its surface is about
\(G = 6.7 \times 10^{-11}\,\mathrm{Nm^2/kg^2}\), mass of the earth is \(6 \times 10^{24}\,\mathrm{kg}\), radius of the earth is \(6.4 \times 10^6\,\mathrm{m}\), g on the earth = \(9.8\mathrm{m/s^2}\)
Answer Details
The earth's gravitational field intensity at its surface can be calculated using the formula: g = G * M / r^2 where G is the gravitational constant, M is the mass of the earth, r is the radius of the earth, and g is the gravitational field intensity at the surface of the earth. Substituting the given values, we get: g = (6.7 × 10^-11 Nm^2/kg^2) * (6 × 10^24 kg) / (6.4 × 10^6 m)^2 g = 9.8 N/kg (approx.) Therefore, the answer is 9.8N/kg.
Question 33 Report
Which of the following statement about the electromagnet shown above is correct?
Answer Details
A - B = S - N.
Also, starting end of the current is south while terminating end is North.
Question 34 Report
The limiting frictional force between two surfaces depends on
I. the normal reaction between the surfaces
II. the area of surface in contact
III. the relative velocity between the surfaces
IV. the nature of the surfaces
Answer Details
- Friction depends on the nature of the surfaces in contact
- Solid friction is independent of the area of the surfaces in contact and the relative velocity between the surfaces.
Question 35 Report
A body was slightly displaced from its equilibrium position. Which one of the following is a condition for its stable equilibrium
Answer Details
The condition for stable equilibrium of a body that has been slightly displaced from its equilibrium position is "an increase in the potential energy of the body." When an object is at its equilibrium position, it has a minimum potential energy. When the object is displaced from its equilibrium position, it has a higher potential energy. For the object to be in stable equilibrium, it must be able to return to its equilibrium position after it has been displaced. If the potential energy of the object increases as it is displaced, it means that the equilibrium position is a point of stable equilibrium. This is because the object will experience a restoring force that will push it back towards its equilibrium position, as the potential energy decreases. Therefore, an increase in potential energy is a condition for a body to be in stable equilibrium after it has been slightly displaced from its equilibrium position. An increase in kinetic energy or height does not necessarily indicate stability, as it depends on the specific situation and other factors at play.
Question 36 Report
Electrons were discovered by
Answer Details
Electrons were discovered by J.J. Thompson. In the late 19th century, he performed a series of experiments using cathode ray tubes, which are glass tubes containing low-pressure gas and electrodes. By applying high voltage, he observed a beam of negatively charged particles traveling from the negative electrode to the positive electrode. He concluded that these particles, which he called "corpuscles," were fundamental units of negative charge and later were renamed electrons. This discovery led to the development of the modern understanding of atomic structure and the electron's role in it.
Question 37 Report
Aluminium is sometimes used as the leaf of an electroscope because it
Answer Details
- Aluminium can be made in thin sheet like Gold.
- the leaf is a thin material that can be diverged easily.
Question 38 Report
A car moving at 20m/s with its horn blowing (f = 1200Hz) is chasing another car going at 15m/s. What is the apparent frequency of the horn as heard by the driver being chased?
Answer Details
| f1 | = | f(v - vo )v - vs | = | 1200(340 - 15)340 - 20 | = | 1.22KHz |
Question 39 Report
Which of the following characteristics of a wave is used in the measurement of the depth of the Sea?
Answer Details
Depth of sea can be measured by echo, a reflected sound waves.
Question 40 Report
A siren having a ring of 200 hole makes 132 rev/min. A jet of air is directed on the set of holes. Calculate the frequency and wavelength in air of the note produced (take v = 350m/s)
Answer Details
n = 200, S = 132 rev/min, v = 350m/s2
| f | = | ns | = | 200 | × | 132 | revmin | × | 1min60s | = | 440Hz |
| λ | = | vf | = | 350440 | = | 0.875m |
