JAMB UTME - Physics - 2017

Answer Details

The action of blotting paper on ink is due to capillarity. Capillarity is the ability of a liquid to flow in narrow spaces, such as the fibers of a piece of blotting paper, against the force of gravity. This is made possible because of the combination of the liquid's surface tension, which acts like a skin on the surface of the liquid, and the wicking action of the fibers in the paper. The fibers in the blotting paper wick the ink from the surface it is on, and the ink is held in the fibers due to the surface tension of the liquid. This is why blotting paper is effective in removing excess ink from surfaces, because it pulls the ink into its fibers and holds it there.

Answer Details

Out of the four options given, black surface will absorb the most radiant heat energy. This is because black surfaces have the ability to absorb all wavelengths of light, including those in the infrared spectrum that are associated with heat. When light strikes a black surface, it is absorbed and converted into heat energy. In contrast, white surfaces reflect all wavelengths of light, including those in the infrared spectrum, which means they reflect heat energy and do not absorb it. Red and blue surfaces fall somewhere in between black and white in terms of their ability to absorb heat energy. Red surfaces tend to absorb more heat than blue surfaces because they reflect less light in the visible spectrum, while blue surfaces tend to reflect more visible light and absorb less heat energy. Therefore, black surfaces are the best at absorbing radiant heat energy, while white surfaces are the worst, and red and blue surfaces fall somewhere in between.

Answer Details

This problem can be solved using Boyle's law, which states that the pressure of a gas is inversely proportional to its volume, as long as the temperature remains constant. Mathematically, Boyle's law can be written as: P1V1 = P2V2 where P1 and V1 are the initial pressure and volume, and P2 and V2 are the final pressure and volume. In this problem, we are given that the initial volume (V1) is 10cm^3 and the initial pressure (P1) is 400cmHg. We are asked to find the final volume (V2) when the pressure (P2) is 200cmHg. Using Boyle's law, we can write: P1V1 = P2V2 400cmHg x 10cm^3 = 200cmHg x V2 Solving for V2, we get: V2 = (400cmHg x 10cm^3) / 200cmHg V2 = 20cm^3 Therefore, the volume of the gas when its pressure is 200cmHg is 20cm^3. Answer option (D) is correct.

Answer Details

The electric field intensity E between two parallel plates of potential difference V separated by a distance d is given by E = V/d. Substituting the given values, we have E = 6.5V/0.35m = 18.57 NC^−1. Therefore, the electric field intensity between the two plates is 18.57 NC^−1. Answer: 18.57NC^−1

Answer Details

The properties of refraction, interference, and diffraction are all common to all types of waves. Refraction is the bending of waves as they pass through a medium with a different density. All types of waves, including sound waves, water waves, and light waves, can refract when they encounter a medium with a different density. Interference occurs when two or more waves interact with each other. This can result in constructive interference, where the waves combine to form a larger wave, or destructive interference, where the waves cancel each other out. All types of waves can interfere with each other. Diffraction is the bending of waves around obstacles or through openings. This phenomenon can be observed when sound waves bend around a corner, or when light waves diffract through a small opening, creating a pattern of light and dark bands. All types of waves can diffract. Therefore, the correct answer is "I, II and III," as all three properties are common to all waves.

Answer Details

Impulse = momentum

Impulse = Force (f) × time (t)

Momentum = mass (m) × velocity (v)

? Ft = Final momentum - initial momentum

FT = mv - mu

Since it is initially at rest u = 0

? 5 × 5 = mv ? m(0)

25 = mv

? Final momentum = 25kgms${}^{?1}$

Answer Details

Answer Details

Internal resistance determine the maximum current that can be supplied

Efficiency = $\frac{r}{R}$ × 100

= $\text{frca}26$ × 100

= 33.3%

Answer Details

1 cycle = 3600 = 2? rad

? 50 cycle = 2 ? rad × 50 = 100 ?rad

? = angular speed = 50 cycles per seconds = 100 ? rads${}_{?1}$

Answer Details

When two mirror are inclined at an angle θ, the number of images formed, n = $\frac{360}{\theta }$ − 1

∴ since $\theta$ = 90o

∴ $\frac{360}{\theta }$ − 1

= 4 − 1

= 3

Answer Details

Work Is only done when an object is moved to a distance.
The ans is C because the man pushed the table to a distance. The rest no work is done.
Ans C

Answer Details

Scalar quantity is a quantity with only magnitude, it has no direction
Tension, weight, impulse are vector quantities because they have direction. Mass is the only scalar quantity there

Answer Details

The instrument that helps to maintain the correct humidity and temperature of a building is an air conditioner. An air conditioner works by removing heat and moisture from the air inside a building, and then circulating cooled and dehumidified air back into the room. It uses a refrigerant to cool the air, and a fan to circulate it. This helps to maintain a comfortable indoor temperature and humidity level, even during hot and humid weather conditions.

Answer Details

For capacitance i n parallel, 2µF and 2µF are in parallel,
their equivalence is 2µF and 2µF = 4µF

The 4µF generated is now in series with the remaining 4µF.

The net capacitance for series connection is

$\frac{1}{C}$ = $\frac{1}{4}$ + $\frac{1}{4}$ = 1 + $\frac{1}{4}$ = $\frac{2}{4}$

C = $\frac{4}{2}$

= 2µF

Answer Details

To calculate the upthrust on an object immersed in a fluid, we need to use Archimedes' principle which states that the upthrust (buoyant force) experienced by an object partially or fully submerged in a fluid is equal to the weight of the fluid displaced by the object. First, let's convert the volume of the object into meters cubed: 50 cm^3 = (50/100)^3 m^3 = 0.0005 m^3 The weight of the liquid displaced by the object is: density of liquid x volume of liquid displaced x acceleration due to gravity = 103 kg/m^3 x 0.0005 m^3 x 10 m/s^2 = 0.515 N Therefore, the upthrust (buoyant force) acting on the object is 0.515 N. So, the correct answer is option C: 0.5N.

Answer Details

The instrument used to measure the relative density of light is a hydrometer. A hydrometer is a device that is designed to measure the density of a liquid by comparing it to the density of water. In order to measure the relative density of light, the hydrometer is placed in a liquid with a known density, such as water. The hydrometer will float at a certain level in the liquid, which indicates the density of the liquid. When measuring the relative density of light, the hydrometer is placed in a liquid that has been made less dense by the addition of a solute, such as sugar or salt. The hydrometer will float at a higher level in the less dense liquid, indicating that the relative density of the light is lower than that of the liquid without the solute. In summary, a hydrometer is the instrument used to measure the relative density of light by comparing it to the density of a liquid with a known density, such as water.

Answer Details

Soldiers march disorderly while crossing a bridge to prevent resonance because when soldiers march in orderly manner across a bridge, they generate a rhythmic oscillation of wave out. The bridge and at a certain point, would start oscillation to the same rhym as that of the marching steps. This oscillation would reach a maximum peak when the bridge can no longer sustain its own strength and hence collapses. So for this reasons, soldier are ordered to march disorderly while crossing a bridge

Answer Details

The specific latent heat of vaporization of steam is the amount of heat energy required to convert one kilogram of water into steam at a constant temperature. The given problem states that 1.13 x 106 J of heat energy is required to convert 15 kg of steam to water. We can use the formula: heat energy = mass x specific latent heat where the mass is 15 kg and the heat energy is 1.13 x 106 J. Rearranging the formula, we get: specific latent heat = heat energy / mass Substituting the values, we get: specific latent heat = 1.13 x 106 J / 15 kg = 7.53 x 104 J/kg Therefore, the specific latent heat of vaporization of steam is 7.53 x 104 J/kg. The correct option is (3): 7.53 x 104 J/kg-1.

Answer Details

Thermal expansion of a solid is majorly advantageous in the use of bimetallic strip in the balance of a watch so as not to lose time

Answer Details

H = mcθ

HP = HQ, θP = 2θ,

mP = $\frac{1}{2}$mQ

∴ HP = mQCPθP, also HQ = mQCQθQ

Since HP = HQ

∴ mPcPθP = mQcPθq

Putting in the conditions

$\frac{1}{2}$mQ × cP × 2θQ = mQ × θQ × cQ

∴ cP = cQ

$\frac{C_p}{C_Q}$= $\frac{1}{1}$

= 1:1

Answer Details

When silicon is doped with a trivalent atom. A p-type semi-conductor will be formed when silicon is doped with a pentavalent atom such as arsenic, a n-type semi-conductor will be formed
Phosphorous is a pentavalent element, so it will produce a o -type semi-conductor

Answer Details

The correct answer is "Molecules of a liquid are stationary" is not correct. This statement is incorrect because the molecules of a liquid are not stationary, they are in constant motion. The molecules in a liquid are able to move past each other, which is why liquids can take the shape of their container. The other statements are all correct. Matter is indeed made up of molecules, and the constant motion of these molecules is what gives matter its physical properties. Brownian motion, which is the random movement of particles in a fluid, is a visible example of the motion of particles in matter and provides evidence for the particle nature of matter.

Answer Details

V = IR from ohms law

I = $\frac{V}{R}$

Since the resistance are in parallel

$\frac{1}{Reff}$ = $\frac{1}{8}$ + $\frac{1}{12}$ + $\frac{1}{6}$

= $\frac{2+3+6}{36}$ = $\frac{11}{36}$

Reff = $\frac{36}{11}$ = 3.27

I = I1 + I2 + I3

= $\frac{V}{Reff}$= $\frac{12}{3.27}$

= 3.669A

I = 3.7A

Answer Details

Barometer is used to measure atmosphere pressure
Thermometer is used to measure temperature
Hygrometer is used to measure relative density of a liquid
Manometer is used to measure the pressure of a gas

Answer Details

To calculate the time taken for a mango fruit to fall from a tree to the ground, we can use the following formula: distance = (1/2) x acceleration x time^2 Where: distance = 20m (the height of the tree) acceleration = 10 m/s^2 (acceleration due to gravity) time = unknown (what we are solving for) Rearranging the formula, we get: time = square root(2 x distance / acceleration) Plugging in the values we get: time = square root(2 x 20 / 10) time = square root(4) time = 2 seconds Therefore, the time taken for a mango fruit to fall from a tree 20 m to the ground is 2 seconds.

Answer Details

An element and its isotope only differ in the number of neutrons. Isotopes are different forms of the same element that have the same number of protons in their nucleus, but a different number of neutrons. The number of protons determines the identity of the element and is called the atomic number, while the number of neutrons in the nucleus is called the mass number. Therefore, the difference between an element and its isotope is only the number of neutrons, not the number of protons or electrons. The number of protons and electrons are the same for all isotopes of a given element.

Answer Details

The formula for calculating the focal length (f) of a thin converging lens in meters using its power (P) in dioptres is: f = 1/P In this problem, the power of the lens is given as 5.0 dioptres. So, substituting this value in the above formula, we get: f = 1/5.0 = 0.2 meters Therefore, the focal length of the lens is 0.2 meters (or 20 centimeters). This means that when parallel light rays pass through this lens, they will converge to a point that is 0.2 meters (20 centimeters) away from the lens. The smaller the focal length of a lens, the greater its ability to converge light, and the stronger its power. So, the correct answer is 0.2 m.

Answer Details

The answer is: sound waves is not an electromagnetic radiation. Electromagnetic radiation is a type of energy that travels through space at the speed of light in the form of waves. It is made up of oscillating electric and magnetic fields, and it includes a wide range of phenomena such as radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, x-rays, and gamma rays. Sound waves, on the other hand, are not electromagnetic radiation. They are mechanical waves that require a medium to travel through, such as air, water, or solids. When an object vibrates, it creates sound waves that travel through the medium and can be heard by our ears. So, while x-rays, radio waves, and sunlight are all examples of electromagnetic radiation, sound waves are not.

Answer Details

To find the power expended, we can use the formula: power = force × velocity Since the man is ascending the stairs at a constant speed, the net force acting on him is zero. However, he is working against the force of gravity, which is pulling him downward with a force equal to his weight, given by: force = mass × acceleration due to gravity = 50 kg × 10 m/s^2 = 500 N The velocity of the man can be found from the distance he covers and the time taken: velocity = distance/time = 5 m/5 s = 1 m/s Thus, the power expended by the man is: power = force × velocity = 500 N × 1 m/s = 500 watts Therefore, the correct answer is option D: 500w.

Answer Details

Consider an inclined plane shown below, as the effort moves along OB, the load moves is lifted up through a vertical height AB

V.R = $\frac{\text{distance moved by effort}}{\text{distance moved by load}}$ = $\frac{OB}{AB}$

But Sinθ = $\frac{opp}{hyp}$ = $\frac{AB}{OB}$

therefore; = $\frac{OB}{AB}$ = $\frac{1}{\sin \theta }$

Answer Details

The semiconductor among the given options is "silicon." Semiconductors are materials that have electrical conductivity between that of a conductor and an insulator. They are widely used in electronics, such as in the construction of computer chips. Copper is a good conductor of electricity and is commonly used in electrical wiring. It is not a semiconductor. Silicon, on the other hand, is one of the most commonly used semiconductor materials in the electronics industry. It has four valence electrons, which allow it to form a crystal lattice structure with other silicon atoms. This structure gives silicon its unique electrical properties that make it useful in electronic devices such as transistors and solar cells. Plastic and iron are not semiconductors. Plastic is an insulator, which means it does not conduct electricity at all, while iron is a conductor, like copper, and does not exhibit the unique electrical properties of a semiconductor.

Answer Details

For a refractive index () = $\frac{\sin \frac{1}{2}(A+D)}{\sin \frac{1}{2}A}$

D = angle of minimum deviation

A = refractive angle of the prism

1.5 = $\frac{\sin \frac{1}{2}(60+D)}{\sin \frac{1}{2}\times 60}$

1.5 = $\frac{\sin \frac{1}{2}(60+D)}{\sin 30}$

Sin $\frac{1}{2}$ (60 + D) = 1.5 * Sin 30

Sin $\frac{1}{2}$ (60 + D) = 0.75

$\frac{1}{2}$ (60 + D) = Sin-1 (0.75)

but Sin-1 (0.75) = 49o

$\frac{1}{2}$ (60 + D) = 49

60 + D = 2 * 49 = 98o

D = 98o - 60o

D = 38o

Answer Details

An atom can be represented thus,

${}_A^{Z}X$ where Z = mass number

A = atomic number

A = number of proton = number of electrons in a free state = 28

Z = number of protons + number of neutrons = 28 + 30 = 58

${}_{28}^{58}X$is the representation

Answer Details

About electric cell
Primary cells are used up gradually often the cells are use and it can't be recharged
Secondary cells or accumulated can be recharged and used for a long period of time and their main advantage is that they have low internal resistance

Answer Details

When the r.m.s value of a source of electricity supply is given as 240V, it means that the peak value of the supply is about 340V. The root-mean-square (r.m.s) value of an AC voltage or current is a way to express the effective or average value of that signal. In the case of a sine wave, the r.m.s value is approximately 0.707 times the peak value of the wave. So, to calculate the peak voltage of a 240V r.m.s supply, we can divide the r.m.s value by 0.707. Using this formula, the peak value of a 240V r.m.s supply can be calculated as: Peak value = r.m.s value / 0.707 = 240V / 0.707 ≈ 339.6V Therefore, the peak value of the supply is approximately 340V. It is important to note that this formula assumes a perfect sine wave, and in reality, the peak value of a voltage signal can fluctuate depending on various factors.

Answer Details

Magnification = $\frac{\text{Length of camera}}{\text{distance of object from pin hole}}$

m = $\frac{12}{60}$

= 0.2

Also magnification m = $\frac{\text{Height of image}}{\text{Height of object}}$

∴ Height of image = m × height of object

= 0.2 × 70

= 14cm

Answer Details

Resistor connected in a parallel have an equivalence given by
$\frac{1}{\text{Reff}}$ = $\frac{1}{3}$ + $\frac{1}{3}$ + $\frac{1}{3}$

= $\frac{1+1+1}{3}$ = $\frac{3}{3}$ = 1

Reff = 1ω

Answer Details

To calculate the efficiency of the block and tackle pulley arrangement, we need to use the formula: efficiency = (load × distance moved by load) / (effort × distance moved by effort) In this case, the load is 200N and the effort is 50N. Since the load is being lifted, its distance moved is equal to the height it is lifted. Let's assume the load is lifted by a distance of 1 meter. Since the effort is being applied over a greater distance due to the pulley system, let's assume it moves a distance of 6 meters (since there are 6 pulleys). Using these values in the formula, we get: efficiency = (200N × 1m) / (50N × 6m) = 0.6667 or 66.67% Therefore, the efficiency of the block and tackle pulley arrangement is 66.67%. This means that only 66.67% of the effort is used to lift the load, with the rest being lost to friction and other factors.

Answer Details

A d.c generator is one in which its current is allowed to flow in one direction even through it may vary in value an a.c generator can only be made to produce a d.c by replacing the two slip rings with a single split ring or commutator.

Answer Details

The formula to calculate the wavelength of a wave is: wavelength = speed of light / frequency where wavelength is the distance between two consecutive peaks or troughs of a wave, frequency is the number of cycles of the wave per second, and the speed of light in air is approximately 3 × 10^8 m/s. In this question, the frequency of the radio wave is given as 600 kHz, which means that it has 600,000 cycles per second. Substituting these values into the formula, we get: wavelength = 3 × 10^8 m/s / 600,000 s^-1 wavelength = 500 m Therefore, the wavelength of the radio wave is 500 meters. The answer is: 5.0 × 10^2 m.