WAEC SSCE - Physics - 2012 (Objective)
Pregunta 1 Informe
Which of the following modes is the most economical method of transmitting electrical power over long distances?
Detalles de la respuesta
The most economical method of transmitting electrical power over long distances is alternating current at high voltage and low current. This is because the power loss in a transmission line is given by the formula P=I²R, where P is the power loss, I is the current and R is the resistance of the transmission line. By transmitting power at high voltage and low current, the current can be reduced, resulting in a lower power loss due to the lower value of I in the formula. This means that more power can be transmitted over longer distances with less loss, resulting in a more efficient and economical method of power transmission.
Pregunta 2 Informe
Which of the following properties is an advantage of lead-acid accumulator over an alkaline accumulator?
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Pregunta 3 Informe
In a R-C circuit
Detalles de la respuesta
In an R-C circuit, a resistor R and a capacitor C are connected in series to an AC voltage source. When an AC voltage is applied to a capacitor in a circuit, it takes some time to fully charge, as the capacitor acts like an open circuit to DC, but passes AC through it. As a result, the current flowing through the circuit will lag the voltage by some angle. This angle is determined by the ratio of the resistance and capacitance in the circuit. Therefore, in a R-C circuit, Vrms leads Irms by 90o.
Pregunta 4 Informe
Which of the following radiations emitted in radioactive decay has momentum, a fairly high penetrating power and is deflected by a magnet?
Detalles de la respuesta
The radiation emitted in radioactive decay that has momentum, a fairly high penetrating power, and is deflected by a magnet is the beta particle. Beta particles are fast-moving electrons or positrons emitted from the nucleus of an atom during radioactive decay. They have a negative charge, a mass of about 1/1836th of a proton, and can penetrate several millimeters of matter. Beta particles can be deflected by a magnetic field, which is a characteristic of charged particles in motion. In contrast, alpha particles are heavy particles consisting of two protons and two neutrons, which have a high ionizing power but are not deflected by a magnetic field. Gamma radiation and X-radiation are both electromagnetic radiation and do not have charge or mass, so they are not deflected by a magnetic field.
Pregunta 5 Informe
When two like charges are brought together, the potential energy of the system formed will
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Pregunta 6 Informe
Which of the following substances is the most volatile at room temperature?
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Pregunta 7 Informe
A bird flies at 10ms\(^{-1}\) for 3s, 15ms\(^{-1}\) for 3s and 20 ms\(^{-1}\) for 4s. Calculate the bird's average speed
Detalles de la respuesta
The average speed is defined as the total distance traveled divided by the total time taken. Let's first calculate the total distance traveled by the bird. Distance traveled in the first 3 seconds = speed × time = 10 ms\(^{-1}\) × 3 s = 30 m Distance traveled in the next 3 seconds = speed × time = 15 ms\(^{-1}\) × 3 s = 45 m Distance traveled in the next 4 seconds = speed × time = 20 ms\(^{-1}\) × 4 s = 80 m Total distance traveled = 30 m + 45 m + 80 m = 155 m Now let's calculate the total time taken: Total time taken = 3 s + 3 s + 4 s = 10 s Therefore, the average speed of the bird is: Average speed = Total distance traveled / Total time taken = 155 m / 10 s = 15.5 ms\(^{-1}\) So the correct option is: - 15.5 ms\(^{-1}\)
Pregunta 8 Informe
A simple pendulum makes 50 oscillations in one minute. Determine its period of oscillation
Detalles de la respuesta
The period of a simple pendulum is the time it takes for one complete oscillation. In this case, we are given that the pendulum makes 50 oscillations in one minute. To find the period, we can use the formula: period = time / number of oscillations We know that the time for one minute is 60 seconds. So, we have: period = 60 seconds / 50 oscillations period = 1.2 seconds Therefore, the period of oscillation is 1.20 seconds, which corresponds to.
Pregunta 9 Informe
When a body is slightly tilted, it is found that its centre of gravity is slightly raised. What is the state of equilibrium of the body?
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Pregunta 10 Informe
A 12\(\Omega\) resistor dissipates 8kJ of heat in 20s. Calculate the current through the resistor
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Pregunta 11 Informe
Six dry cells each of e.m.f. 2.0 and internal resistance of 1.0\(\Omega\) are connected in parallel across a load of 3.0\(\Omega\). Calculate the effective current in the circuit.
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Pregunta 13 Informe
Which of the following properties of waves is exclusive to transverse waves?
Detalles de la respuesta
Polarization is the property of waves that is exclusive to transverse waves. Polarization refers to the orientation of the oscillations of the wave, which can be either perpendicular or parallel to the direction of wave propagation. In a transverse wave, the oscillations are always perpendicular to the direction of propagation. This means that transverse waves can be polarized, while longitudinal waves cannot. Reflection, interference, and diffraction can occur in both transverse and longitudinal waves.
Pregunta 14 Informe
A piece of copper of mass 20g at a temperature of 110°C was dropped into a mixture of ice and water at 0°C. If the final steady temperature of the mixture is 0°C . Calculate the amount of ice that melted [Specific heat capacity of copper = 0.4 Jg\(^{-1}\)K\(^{-1}\), specific latent heat of fusion of ice = 330Jg\(^{-1}\)]
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Pregunta 15 Informe
An inductor is connected to a 24V, 50Hz mains supply. If the current through the inductor is 1.5A, calculate the inductance of the inductor (\(\pi = \frac{22}{7}\))
Detalles de la respuesta
The formula for the inductive reactance is XL = 2πfL, where XL is the inductive reactance in ohms, f is the frequency in Hertz and L is the inductance in Henrys. We are given that the mains supply has a frequency of 50Hz, and that the current through the inductor is 1.5A. We also know that the voltage across the inductor is V = I XL, where V is the voltage in volts. The voltage across the inductor is given as 24V, so we can use Ohm's law to find the inductive reactance: XL = V / I = 24V / 1.5A = 16Ω We can now use the formula XL = 2πfL to find the inductance: L = XL / 2πf = 16Ω / (2π x 50Hz) = 0.051H ≈ 5.1 x 10-2H Therefore, the inductance of the inductor is approximately 5.1 x 10-2H. The correct option is (d).
Pregunta 16 Informe
An object is dropped from the top of a tower. If it takes 4s for it to reach the ground, calculate the height of the tower.(g = 10 ms-2, ignore air resistance)
Detalles de la respuesta
When an object is dropped from rest, it falls under the influence of gravity. The distance it falls in time t is given by the formula: s = (1/2)gt² where g is the acceleration due to gravity. In this question, we are given t = 4s and g = 10 ms⁻². Substituting these values into the formula above, we get: s = (1/2) x 10 ms⁻² x (4 s)² = 80 m So, the height of the tower is 80 meters. Therefore, the correct answer is 80m.
Pregunta 17 Informe
Two similar cells are used to light two similar lamps as illustrated in the diagrams above. In which of the circuit diagrams are the lamps brightest?
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Pregunta 18 Informe
The movement of fluid up or down a narrow tube is
Detalles de la respuesta
The movement of fluid up or down a narrow tube is capillarity. Capillary action, also known as capillarity, is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. This occurs because of the combination of two opposing forces: adhesion, the attraction between the liquid molecules and the inner surface of the tube, and cohesion, the attraction between the liquid molecules themselves. When the adhesion force is greater than the cohesion force, the liquid is pulled up the tube, and when the cohesion force is greater, the liquid is pushed down the tube. Capillarity is responsible for many natural phenomena, such as the ability of plants to transport water from their roots to their leaves, as well as some man-made ones, such as the operation of wicks in candles and the ink in fountain pens.
Pregunta 19 Informe
An object is placed at a point X between the focal point F and the optical centre C of a diverging lens. If F is the focal point on the other side of the lens, the image of the object is formed between
Detalles de la respuesta
For a diverging lens, the image formed is always virtual, upright and smaller than the object. When the object is placed between the focal point and the optical center of the lens, the image formed will always be virtual, upright and will appear on the same side of the object. Also, the image will be formed by the diverging lens itself, so it will be between the lens and the focal point F on the same side as the object. Therefore, the correct option is (B) X and C.
Pregunta 20 Informe
A girl stands on a scale in a lift. If the reading on the scale is less than her weight, then the lift is moving
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Pregunta 21 Informe
The tendency for a stationary body to continue to remain at rest when a force is applied to it is known as
Detalles de la respuesta
The tendency for a stationary body to continue to remain at rest when a force is applied to it is known as inertia. Inertia is a fundamental property of matter that resists changes in motion, whether it is a stationary object or an object in motion. It is often described as the resistance of an object to changes in its state of motion, and it is directly related to an object's mass. The greater the mass of an object, the greater its inertia and the more force it will take to move it from a stationary position. This property of inertia is the reason why a heavy object requires more force to move than a light one.
Pregunta 22 Informe
When two waves are superimposed on each other, the following occurrences are possible, except
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Pregunta 23 Informe
A metal sheet of area 100cm\(^2\) was heated through 70°C. Calculate its new area if the linear expansivity of the metal is 0.000017K\(^{-1}\).
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Pregunta 24 Informe
the core of a transformer is usually laminated in order to
Detalles de la respuesta
The core of a transformer is laminated in order to reduce eddy currents. Eddy currents are created by a magnetic field that is changing over time, inducing a current in the core. This current can cause energy loss and heating of the core, leading to inefficiencies in the transformer. Laminating the core creates many thin layers of material, each separated by a thin layer of insulation. This structure reduces the size of the current loops that can form and reduces the resistance of the current flow in the material. This reduction in eddy current also reduces energy loss, leading to greater efficiency of the transformer.
Pregunta 25 Informe
The diagram above illustrates trapped air in a syringe placed in water that is gradually heated. It is observed that the piston rises as the temperature of the water rises. Which of the following statements explains this observation?
Detalles de la respuesta
As the temperature of the water in the syringe increases, the water molecules transfer some of their thermal energy to the trapped air molecules. This causes the air molecules to move faster, collide more frequently, and exert more pressure on the walls of the syringe. The increase in pressure of the trapped air forces the piston to move upwards, against the external atmospheric pressure. Therefore, the correct statement explaining the observation is "molecules of trapped air expands more".
Pregunta 26 Informe
The time of flight for a projectile motion is given by the expression
Detalles de la respuesta
The time of flight is the total time taken by a projectile to complete its motion before it returns to the same level from which it was projected. The given expression for time of flight involves the initial velocity of the projectile (U), the angle of projection (theta) and the acceleration due to gravity (g). Therefore, the expression for the time of flight of a projectile is: \(\frac{2U sin \theta}{g}\) Option (C) matches the given expression and is the correct answer.
Pregunta 27 Informe
A body is pulled through a distance of 500m by a force of 20N. If the power developed is 0.4kW, calculate the time for which the force acts
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Pregunta 28 Informe
Which of the following devices is used to determine the relative density of an acid?
Detalles de la respuesta
The device used to determine the relative density of an acid is a hydrometer. A hydrometer is an instrument used to measure the density or specific gravity of a liquid. It works based on Archimedes' principle, which states that the buoyant force on an object is equal to the weight of the fluid displaced by the object. The hydrometer consists of a glass tube with a bulb at the bottom, and a scale to measure the density. When the hydrometer is placed in the acid, it floats and sinks to a certain level depending on the density of the acid. The density is then read off the scale at the level where the surface of the liquid intersects the scale on the hydrometer. Therefore, a hydrometer is used to determine the relative density of an acid.
Pregunta 29 Informe
The thermopile is a device for detecting
Detalles de la respuesta
A thermopile is a device that is used to detect radiant energy. When radiant energy is absorbed by a thermopile, it generates a small voltage, which can be measured by a voltmeter. This is because the thermopile is made up of a series of thermocouples, which are devices that generate a voltage when there is a difference in temperature between their ends. When the thermopile absorbs radiant energy, it causes a temperature difference between the ends of the thermocouples, which in turn generates a voltage. Therefore, the correct option is: radiant energy.
Pregunta 30 Informe
An atom in an excited state is one whose
Detalles de la respuesta
An atom in an excited state is one whose electrons have moved to higher energy levels. When an atom absorbs energy, its electrons move to higher energy levels, or orbitals, which are farther from the nucleus. When an electron moves from a lower energy level to a higher energy level, the atom is said to be in an excited state. Eventually, the electrons return to their original energy level by emitting energy in the form of electromagnetic radiation.
Pregunta 31 Informe
The magnetic relay is a device used for
Detalles de la respuesta
The magnetic relay is a device used for controlling another circuit carrying a larger current. It consists of an electromagnet, a spring-loaded armature, and a set of contacts. When a current passes through the coil of the electromagnet, it generates a magnetic field which attracts the armature and causes it to move, closing or opening the contacts. This can be used to switch on or off a circuit carrying a larger current, or to switch between different circuits. The magnetic relay is commonly used in applications such as industrial automation, power systems, and telecommunications.
Pregunta 32 Informe
An object is placed 10cm from a converging lens of foal length 15cm. Calculate the magnification of the image formed
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Pregunta 33 Informe
Which of the following sets of coloured light is/are secondary colours i. Red, Blue and green ii. Blue, cyan and magneta iii. Green, Magenta and yellow, IV Yellow, Cyan and Magenta
Detalles de la respuesta
The secondary colors of light are the colors that result from mixing two primary colors of light. The three primary colors of light are red, green, and blue. Option i consists of two primary colors of light (red and blue) and a secondary color of light (green). Therefore, it is not a set of secondary colors of light. Option ii consists of one primary color of light (blue) and two secondary colors of light (cyan and magenta). Therefore, it is a set of secondary colors of light. Option iii consists of two secondary colors of light (magenta and yellow) and a primary color of light (green). Therefore, it is not a set of secondary colors of light. Option iv consists of three secondary colors of light (cyan, magenta, and yellow). Therefore, it is a set of secondary colors of light. Thus, the correct answer is option ii and iv only.
Pregunta 34 Informe
A telescope is said to be in normal adjustment when the
Detalles de la respuesta
A telescope is said to be in normal adjustment when the objective focal point coincides with that of the eyepiece. This means that the light rays coming in from the object being observed converge to a point at the same location where the eyepiece is positioned, allowing the viewer to see a magnified image. If the objective focal point is too far away from the eyepiece or if the focal lengths of the objective and eyepiece are not matched, the viewer will not be able to see a clear image. Therefore, adjusting the telescope to achieve normal adjustment is crucial for obtaining a clear, magnified image of the object being observed.
Pregunta 35 Informe
A block of wood of density 0.6 gcm\(^{-3}\), weighing 3.06N in air, floats freely in a liquid of density 0.9 gcm\(^{-3}\). Calculate volume of the portion immersed (g = 10ms\(^{-2}\))
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Pregunta 36 Informe
The S.I unit of heat is
Detalles de la respuesta
The SI unit of heat is the joule (J). Heat is a form of energy that is transferred from one body to another as a result of a difference in temperature. The amount of heat transferred is measured in joules, which is the amount of energy required to move an object with a force of one newton for a distance of one meter in the direction of the force. Therefore, the correct option is (a) joule. Kelvins (K) are used to measure temperature, watts (W) measure power and amperes (A) measure electric current.
Pregunta 37 Informe
A ray of light passes from air to water to glass to air. Given that the refractive index for light passing from air to water is \(\frac{4}{3}\) and air to glass is \(\frac{3}{2}\), calculate the refractive index of glass relative to water
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Pregunta 38 Informe
Which of the following statements about X-rays is correct? X-rays
Detalles de la respuesta
X-rays are produced when a metal target is used to block fast moving electrons. When high-speed electrons are fired at a metal target, they collide with the atoms in the target and produce X-rays. X-rays have short wavelengths and are highly penetrating, which makes them useful in medical imaging and materials analysis. Therefore, the correct statement among the options is "are produced when a metal target is used to block fast moving electrons."
Pregunta 39 Informe
Which of the following arrangements of radiations is in the order of decreasing penetrating power?
Detalles de la respuesta
The penetrating power of radiation is a measure of its ability to penetrate through matter. The more penetrating the radiation is, the farther it can travel through matter. In general, the penetrating power of radiation is inversely proportional to its ionizing power. - Alpha particles (\(\alpha\)): They are positively charged and have a large mass. They have a low penetrating power and are stopped by a sheet of paper or a few centimeters of air. - Beta particles (\(\beta\)): They are negatively charged and have a smaller mass compared to alpha particles. They have a higher penetrating power than alpha particles and can penetrate through a few millimeters of aluminum or several meters of air. - Gamma rays (\(\gamma\)): They are neutral and have no mass. They have the highest penetrating power and can penetrate through several centimeters of lead or many meters of concrete. Therefore, the correct order of decreasing penetrating power is \(\gamma, \beta, \alpha\). lists the radiations in this order.
Pregunta 40 Informe
The sound heard by a person after the reflection of the sound generated by him is called
Detalles de la respuesta
The sound heard by a person after the reflection of the sound generated by him is called an "echo." An echo occurs when sound waves bounce off a hard surface and return to the listener's ear after a noticeable delay. The delay between the original sound and the reflected sound is called the "echo time." The quality of the echo is determined by the distance between the sound source and the reflecting surface, as well as the shape and size of the reflecting surface.
Pregunta 41 Informe
A metal with a work function of 3.0ev is irradiated with ultraviolet light of energy 4.0 ev. The kinetic energy of the ejected electron is
Detalles de la respuesta
The work function of a metal is the minimum amount of energy required to remove an electron from the surface of the metal. When the metal is irradiated with light of energy greater than the work function, electrons are emitted from the metal surface. The excess energy of the light is used to give kinetic energy to the ejected electron. In this case, the metal has a work function of 3.0eV and is irradiated with ultraviolet light of energy 4.0eV. Since the energy of the light is greater than the work function, electrons will be ejected from the metal surface. The kinetic energy of the ejected electron can be found by subtracting the work function from the energy of the incident light: Kinetic energy of ejected electron = Energy of incident light - Work function = 4.0eV - 3.0eV = 1.0eV Therefore, the kinetic energy of the ejected electron is 1.0eV.
Pregunta 42 Informe
The derived unit of pressure can be expressed as
Detalles de la respuesta
Pressure is defined as force per unit area. Mathematically, pressure (P) can be expressed as P = F/A, where F is force and A is the area. The unit of force is newton (N) and the unit of area is square meter (m2). Therefore, the unit of pressure is N/m2. This can be further simplified as kg m/s2 / m2 which gives kg m-1s-2. Therefore, option (B) is the correct answer.
Pregunta 43 Informe
An object of height 2.5cm is places 20cm from a convex mirror of focal length 10cm. Calculate the height of its image.
Detalles de la respuesta
The given problem is related to optics and involves the use of the mirror formula. According to the mirror formula, 1/f = 1/v + 1/u where, f = focal length of the mirror u = object distance v = image distance The magnification produced by the mirror is given by the ratio of the height of the image to the height of the object. magnification = height of image / height of object From the problem statement, height of object (h) = 2.5 cm distance of object from the mirror (u) = 20 cm focal length of the mirror (f) = 10 cm Using the mirror formula, we can find the image distance (v) as: 1/10 = 1/v + 1/20 => 1/v = 1/10 - 1/20 => v = 20 cm The image is formed at a distance of 20 cm from the mirror. Now, using the magnification formula, we can find the height of the image as: magnification = height of image / height of object => height of image = magnification * height of object The magnification produced by a convex mirror is always less than 1. Therefore, the image formed will be smaller than the object. For a convex mirror, magnification = -v/u Substituting the given values, we get: magnification = -20/20 = -1 Therefore, the height of the image is given by: height of image = magnification * height of object => height of image = -1 * 2.5 cm => height of image = -2.5 cm Since the height of the image cannot be negative, we take its absolute value: height of image = |-2.5 cm| = 2.5 cm Hence, the height of the image is 2.5 cm. Therefore, the correct option is (a) 2.5 cm.
Pregunta 44 Informe
Two capacitors, each of capacitance 2\(\mu\)F are connected in parallel. If the p.d across them is 120V, calculate the charge on each capacitor
Detalles de la respuesta
The total capacitance of two capacitors connected in parallel is given by the sum of individual capacitances, which is 2μF + 2μF = 4μF. The charge on a capacitor is given by the product of its capacitance and the potential difference across it, which is Q = CV. Using the formula Q = CV and substituting the values, we get: Q = 4μF x 120V = 480μC Since there are two capacitors connected in parallel, the total charge is divided equally between them. Therefore, the charge on each capacitor is: Q/2 = 480μC/2 = 240μC So the answer is 2.4 x 10-4C.
Pregunta 45 Informe
A resultant force of magnitude 15N acts on a body of mass 250g. Calculate the magnitude of the acceleration
Detalles de la respuesta
The magnitude of the acceleration is given by the formula: acceleration = resultant force / mass In this question, the resultant force is given as 15N and the mass is 250g which is equivalent to 0.25kg. Therefore, acceleration = 15N / 0.25kg = 60.00ms-2 Hence, the correct option is 60.00ms-2.
Pregunta 46 Informe
Which of the following factors decreases the rate of evaporation of a liquid?
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Pregunta 47 Informe
A metal ball of weight W falls through a column of glycerine of viscosity V. If the ball experiences an upthrust U and terminal velocity is attained, then
Detalles de la respuesta
When the metal ball falls through the column of glycerine, it experiences both weight and upthrust, which opposes the motion of the ball. Eventually, the forces will be balanced and the velocity of the ball becomes constant, which is called terminal velocity. At this point, the forces on the ball are in equilibrium, which means that the weight of the ball (W) is equal to the upthrust (U) plus the viscous drag force (V). Therefore, the correct answer is: W = U + V Option (B)
