JAMB UTME - Physics - 2017 | Green Bridge CBT

Question 1 Report

Calculate the angle of minimum deviation of a 60o prism of a refractive index [sin-10.75 = 49o]

38.00o

19.47o

16.25o

49o

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

Read lesson note on Properties Of Waves: Reflection, Refraction, Diffraction (WAEC)

Properties Of Waves: Reflection, Refraction, Diffraction

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Question 2 Report

From the diagram above, calculate the total current in the circuit

5.0A

3.7A

4.5A

4.0A

Answer Details

V = IR from ohms law

I = $\frac{V}{R}$

Since the resistance are in parallel

$\frac{1}{R e f f}$ = $\frac{1}{8}$ + $\frac{1}{12}$ + $\frac{1}{6}$

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

Reff = $\frac{36}{11}$ = 3.27

I = I1 + I2 + I3

= $\frac{V}{R e f f}$ = $\frac{12}{3.27}$

= 3.669A

I = 3.7A

Read lesson note on Current Electricity (JAMB)

Current Electricity

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Question 3 Report

Calculate the time taken for a mango fruit that fall from the tree 20 m to the ground [g = 10 ms-2]

10s

5s

4s

2s

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.

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Motion

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Question 4 Report

Which is the incorrect formula for a body accelerating uniformly?

a = v2 − u

\frac{2}{2}

v2 = u2 + 2as

s =

\frac{1}{2}

ut + at2

v2 − u2= 2as

Answer Details

s =

\frac{1}{2}

ut + at2 is a wrong equation, it should be s = ut +

\frac{1}{2}

at2

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Rectilinear Acceleration

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Question 5 Report

From the diagram above, calculate the energy stored in the capacitor

4.0 x 10

^{- 2}

J

4.0 x 10

^{- 4}

J

8.0 x 10

^{- 4}

J

8.0 x 10

^{- 2}

J

Answer Details

c = 8µF, v = 10v

Energy stored = $\frac{1}{2}$ cv2

= $\frac{1}{2}$ × (8 × 10− 6) × 102

= 4 × 10 $^{- 4}$

Read lesson note on Capacitors (JAMB)

Capacitors

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Question 6 Report

The net capacitance in the circuit above is

80µF

6.0µF

4.0µF

2.0µF

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

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Read lesson note on Measurements And Units (JAMB)

Capacitors

Measurements And Units

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Question 7 Report

Which of the following is a semiconductor

copper

silicon

plastic

Iron

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.

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Question 8 Report

Which of the following is not an electromagnetic radiation?

x - ray

Radio waves

sunlight

sound waves

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.

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Electromagnetic Waves: Types Of Radiation In Electromagnetic Spectrum

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Question 9 Report

A block and tackle pulley arrangement has 6 pulleys in which an effort of 50N supports a load of 200N, calculate the efficiency of the machine

80.0%

76.6%

66.7%

60.7%

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.

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Simple Machines

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Question 10 Report

Calculate the specific latent heat of vaporization of steam of 1.13 x 106J pf heat energy is required to convert 15kg of it to water.

7.53 x 105 Jkg

^{- 1}

7.53 x 10-2Jkg

^{- 1}

7.53 x 104Jkg

^{- 1}

7.53 x 10-3Jkg

^{- 1}

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.

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Quantity Of Heat

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Question 11 Report

If silicon is doped with phosphorus, what type of semiconductor material will be formed?

Zener material

P-n junction

n-type

p-type

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

Read lesson note on Structure Of The Atom (Nigeria Only) (WAEC)

Structure Of The Atom (Nigeria Only)

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Question 12 Report

It is known that a neutron exists in a light atomic nucleus

Which of the following also exists in the nucleus?

An electron

A β - particle

β - particle

proton

Answer Details

A neutron is a subatomic particle that has no electric charge and is found in the nucleus of an atom along with protons. Therefore, the correct option is: - proton An electron is a negatively charged subatomic particle that orbits around the nucleus of an atom. A β- particle, also known as a beta particle, is an electron or a positron emitted during radioactive decay. Both of these particles are not found in the nucleus of an atom. On the other hand, a proton is a positively charged subatomic particle that is also found in the nucleus of an atom along with neutrons. The number of protons in the nucleus determines the atomic number of the element. Hence, a proton also exists in the nucleus along with a neutron. In summary, the only subatomic particle that exists in the nucleus along with a neutron is a proton.

Read lesson note on Structure Of The Nucleus (WAEC)

Read lesson note on Structure Of The Atom (Nigeria Only) (WAEC)

Structure Of The Nucleus

Structure Of The Atom (Nigeria Only)

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Question 13 Report

The S.I unit of moment of a force is

kgm

µm

Jm

µm

^{- 1}

Answer Details

Moment of a force is the product of a force and the perpendicular distance from the line of action of the force
Moment = force × distance
= N × m
= Nm

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Question 14 Report

Calculate the electric field intensity between two plates of potential difference 6.5V when separated by a distance of 35cm.

18.57NC

^{- 1}

53.06NC

^{- 1}

2.28NC

^{- 1}

0.80NC

^{- 1}

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

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Electric Field

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Question 15 Report

Which of the following operations can be used to convert an alternative current dynamo into a direct current dynamo

number of turns in the coil is increased

strength of the field magnet is increased

slip rings are replaced with split ring cummutator

coil is wound on a soft iron armature

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.

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Capacitors

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Question 16 Report

Under what conditions are cathode rays produced in a discharge tube?

High pressure and low voltage

High pressure and high voltage

Low pressure and low voltage

Low pressure and high volatge

Answer Details

Cathode rays are streams of electrons that are emitted from the cathode of a discharge tube. A discharge tube is a partially evacuated glass tube with two metal electrodes: a cathode (negative electrode) and an anode (positive electrode). When a voltage is applied across the electrodes, a current flows through the gas in the tube, and cathode rays can be produced. The conditions required to produce cathode rays in a discharge tube are low pressure and high voltage. When the gas inside the tube is at a low pressure, there are fewer gas molecules to collide with the electrons emitted from the cathode. This means that the electrons can travel a longer distance without colliding with other particles, which allows them to form a visible beam of cathode rays. The high voltage applied to the electrodes causes a potential difference between the cathode and anode. This potential difference accelerates the electrons emitted from the cathode towards the anode. The faster the electrons travel, the more kinetic energy they have, and the more likely they are to collide with other gas molecules in the tube. These collisions can cause the gas molecules to become ionized, which can create a cascade effect, leading to the production of more electrons and the formation of a bright beam of cathode rays. Therefore, the correct answer is: Low pressure and high voltage.

Read lesson note on Structure Of The Atom (Nigeria Only) (WAEC)

Read lesson note on Electrostatics (JAMB)

Structure Of The Atom (Nigeria Only)

Electrostatics

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Question 17 Report

Which of the following statements is NOT correct?

Molecules of a liquid are stationary

Brownian motion is an evidence of particle nature of matter

Matter is made up of molecules

The molecules of matter are in constant motion

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.

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Thermal Expansion

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Question 18 Report

Which of the following representations is correct for an atom X with 28 electrons and 30 neutrons?

5828X

3028X

2830X

5830X

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

Read lesson note on Structure Of The Atom (Nigeria Only) (WAEC)

Structure Of The Atom (Nigeria Only)

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Question 19 Report

When two mirrors are placed at an angle of 900 to each other, how many images will be formed when an object is placed in front of the mirrors

5

4

3

2

Answer Details

When two mirror are inclined at an angle θ, the number of images formed, n =

\frac{360}{θ}

− 1

∴ since $θ$ = 90o

∴ $\frac{360}{θ}$ − 1

= 4 − 1

= 3

Read lesson note on Properties Of Waves: Reflection, Refraction, Diffraction (WAEC)

Read lesson note on Electrostatics (JAMB)

Properties Of Waves: Reflection, Refraction, Diffraction

Electrostatics

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Question 20 Report

Three 3ω resistance are connected in parallel what is the equivalent resistance?

1ω

9ω

3ω

0.33ω

Answer Details

Resistor connected in a parallel have an equivalence given by

\frac{1}{Reff}

=

\frac{1}{3}

+

\frac{1}{3}

+

\frac{1}{3}

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

Reff = 1ω

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Scalars And Vectors

Equilibrium Of Forces

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Question 21 Report

How can energy loss be minimized through Eddy-current?

By using high resistance wire

By using insulated soft iron wires

By using low resistance wires

Bu using turns of wires

Answer Details

Eddy currents are produced by the varying flux cathode, the iron core of an equipment thus reducing efficiency due to power consumption. It can be reduced by laminating the core by breaking up the path of eddy current or by increasing the resistance of the core
Usage of insulated soft iron wire is to reduce hysteresis loss
Usage of low resistance wire (thick wire) is to reduce I2R loss
Usage of thick wire is to reduce leakage heat loss due to leakage of magnetic flux
Thus the correct answer is to use high resistance wire or thin wire

Read lesson note on Electrostatics (JAMB)

Electrostatics

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Question 22 Report

A string of length 5cm is extended by 0.04m when a load of 0.8kg is suspended at the end. How far will it extend if a force of 16N is applied? [$g = 10ms^{-2}$]

0.04m

0.12m

0.01m

0.08m

Answer Details

The extension of a string when a load is suspended from it is given by Hooke's Law which states that the extension is proportional to the force applied. The proportionality constant is called the spring constant, represented by k. Mathematically, we can express this relationship as: F = kx where F is the force applied, x is the extension, and k is the spring constant. To solve this problem, we need to find the spring constant, k, of the string. We can use the information given in the problem to calculate k as follows: k = F/x where F is the force applied and x is the extension. We are given that the string of length 5cm (which is 0.05m) is extended by 0.04m when a load of 0.8kg is suspended at the end. We can convert the mass to force using the formula F = mg, where g is the acceleration due to gravity (g = 10ms^-2). F = 0.8kg × 10ms^-2 = 8N Using the formula for the spring constant, we get: k = F/x = 8N / 0.04m = 200N/m Now, we can use this spring constant to find the extension when a force of 16N is applied. Again, we can use the formula F = kx and rearrange it to solve for x: x = F/k Plugging in the values, we get: x = 16N / 200N/m = 0.08m Therefore, the string will extend by 0.08m when a force of 16N is applied. The answer is (D) 0.08m.

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Question 23 Report

I. Refraction II. Interference III. Diffraction
Which of the above properties are common to all waves?

II and III only

I, II and III

I and II only

I and III only

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.

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Production And Propagation Of Waves

Types Of Waves

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Question 24 Report

A radio station broadcast at a frequency of 600KHZ. If the speed of light in air is $3 \times 108ms^{-1}$. Calculate the wavelength of the radio wave

2.20 × 10

^{3}

m

5.0 × 10

^{2}

m

5.0 × 10

^{5}

m

11.8 × 10

^{11}

m

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.

Read lesson note on Properties Of Waves: Reflection, Refraction, Diffraction (WAEC)

Properties Of Waves: Reflection, Refraction, Diffraction

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Question 25 Report

Determine the focal length of a thin converging lens if the power is 5.0 dioptres

0.1 m

0.2 m

2.0 m

2.5 m

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.

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Gravitational Field

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Question 26 Report

Why do soldiers march disorderly while crossing a bridge?

To prevent resonance on the bridge

To set the bridge into resonance

To make the b ridge collapse

To spread their weight evenly on the bridge

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

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Read lesson note on Pressure (JAMB)

Temperature And Its Measurement

Pressure

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Question 27 Report

Which of the following is correct about an electric cell?

Primary cell produces a large current for a long time

Secondary cell has a very high internal resistance

Primary cell has a very low internal resistance

Secondary cell has a very low internal resistance

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

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Read lesson note on Electric Cells (JAMB)

Current Electricity

Electric Cells

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Question 28 Report

A constant force of 5N acts for 5 seconds on a mass of 5kg initially at rest. Calculate the final momentum

125kgms?1

25kgms?1

15kgms?1

0kgms?1

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 $^{- 1}$

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Newton’s Laws Of Motion

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Question 29 Report

The volume of a fixed mass of gas is 10cm3 when its pressure is 400cmHg. Determine the volume of the gas when its pressure is 200cmHg.

30cm3

40cm3

50cm3

20cm3

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.

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Question 30 Report

An element and its isotope only differ in the number of

protons

electrons

ions

neutrons

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.

Read lesson note on Structure Of The Atom (Nigeria Only) (WAEC)

Structure Of The Atom (Nigeria Only)

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Question 31 Report

Calculate the upthrust on an object of volume 50cm3 which is immersed in liquid of density 103kgm-3 [g = 10ms-2]

0.8N

2.5N

0.5N

1.0N

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.

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Measurements And Units

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Question 32 Report

Which of the following surfaces will absorbs radiant heat energy heat?

white

red

black

blue

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.

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Heat Energy

Work, Energy And Power

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Question 33 Report

The thermal expansion of a solid is an advantage in

Balance wheel of a watch

Construction of steel rail lines

Construction of large steel bridges

Fitting of tyres on wheels

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

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Thermal Expansion

Elasticity

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Question 34 Report

What is the cost of running seven 40 W lamps and five 80 W la mps for 12 hours of the electrical energy cost N7.00kWk?

N80.00

N45.36

N65.00

N57.12

Answer Details

To calculate the cost of running the lamps, we need to determine the total energy consumed in kilowatt-hours (kWh) and multiply it by the cost of electrical energy per kWh. First, let's calculate the total power consumption of the lamps: Total power consumption = (7 x 40 W) + (5 x 80 W) = 280 W + 400 W = 680 W Next, let's convert the power consumption to kWh: Energy consumption = (680 W / 1000) x 12 hours = 8.16 kWh Finally, let's calculate the cost of running the lamps: Cost = Energy consumption x Cost of electrical energy per kWh Cost = 8.16 kWh x N7.00/kWh = N57.12 Therefore, the cost of running seven 40 W lamps and five 80 W lamps for 12 hours at an electrical energy cost of N7.00/kWh is N57.12. The correct answer is option D.

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Current Electricity

Electric Cells

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Question 35 Report

A cell of internal resistance 2 π supplies current to a 6 π resistor. The efficiency of the cell is

12.0%

25.0%

33.3%

75.0%

Answer Details

Internal resistance determine the maximum current that can be supplied

Efficiency = $\frac{r}{R}$ × 100

= $\frca 26$ × 100

= 33.3%

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Current Electricity

Electric Cells

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Question 36 Report

Under which of the following conditions is work done?

A man supports a heavy food above his head with his hands

A boy climbs onto a table

A man pushes unto a table

A woman holds a pot of water

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

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Work, Energy And Power

Equilibrium Of Forces

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Question 37 Report

The action of blotting paper on ink is due to

diffusion

osmosis

capillarity

surface tension

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.

Read lesson note on Properties Of Waves: Reflection, Refraction, Diffraction (WAEC)

Read lesson note on Simple A.C Circuits (JAMB)

Read lesson note on Pressure (JAMB)

Properties Of Waves: Reflection, Refraction, Diffraction

Simple A.C Circuits

Pressure

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Question 38 Report

The instrument to measure the relative density of light is

thermometer

hydrometer

spring balance

beaker

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.

Read lesson note on Pressure (JAMB)

Pressure

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Question 39 Report

Which of the following instruments helps to maintain the correct humidity and temperature of a building?

A compressor

A refrigerator

Air blower

Air conditioner

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.

Read lesson note on Electromagnetic Field (Part 1) (WAEC)

Read lesson note on Gravitational Field (WAEC)

Electromagnetic Field (Part 1)

Gravitational Field

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Question 40 Report

A block and tackle pulley arrangement has 6 pulleys in which an effort of 50N supports a load of 200N, calculate the efficiency of the machine

80.0%

76.6%

66.7%

60.7%

Simple Machines

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