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Question 1 Rapport
One of these is not the use of an electroscope
Détails de la réponse
Measuring ionization current in air:
This is typically not a function of an electroscope. While it can detect charge, it does not measure ionization currents, which require specialized equipment like an ionization chamber.
Question 2 Rapport
If the S.V.P of water vapour was 13.5mmHg at 33ºC and 7.3mmHg at 7ºC. Find the percentage relative of the air on a day when average air temperature was 33ºC and dew point was 7ºC.
Détails de la réponse
To calculate the percentage relative humidity of the air, we use the relationship between the saturation vapour pressure (SVP) and the actual vapour pressure. The formula for relative humidity is:
Relative Humidity (%) = (Actual Vapour Pressure / Saturation Vapour Pressure) * 100
In this problem, the "dew point" refers to the temperature at which air becomes saturated with moisture and water begins to condense. At the dew point, the actual vapour pressure is equal to the saturation vapour pressure at that dew point temperature.
From the problem, we have:
The actual vapour pressure of the air is equal to the SVP at the dew point, which is 7.3 mmHg.
Now we calculate the percentage relative humidity using the formula:
Relative Humidity (%) = (7.3 mmHg / 13.5 mmHg) * 100
Carrying out the calculation:
Relative Humidity (%) = (7.3 / 13.5) * 100 = 0.5407 * 100 = 54.07%
Rounding to the nearest whole number, we get **54%**. Therefore, the percentage relative humidity of the air is 54%.
Question 3 Rapport
Which of the following structures enables the exchange of gases in insects?
Détails de la réponse
In insects, the structure responsible for the exchange of gases is the tracheae. Insects have a unique respiratory system where air is taken in through tiny openings called spiracles located on the surface of their body.
The air then travels directly into a network of tubes known as the tracheae. The tracheae branch out extensively throughout the insect's body, allowing oxygen to diffuse directly to the insect's tissues and cells. The carbon dioxide produced in the cells travels back through the tracheae and exits the body through the spiracles.
Other structures like the skin, Malpighian tubules, and flame cells have different functions:
Thus, the correct answer is the tracheae as they specifically enable the exchange of gases in insects.
Question 4 Rapport
The energy of light of frequency 2.0 x 1015 Hz is (h = 6.63 x 10−34 Js)
Détails de la réponse
To determine the energy of light given its frequency, we can utilize the formula:
E = h × f
Where:
E is the energy of the photon in joules (J)
h is Planck's constant, approximately 6.63 × 10-34 J·s
f is the frequency of light in hertz (Hz)
Given the frequency f = 2.0 × 1015 Hz, we can substitute the known values into our equation:
E = 6.63 × 10-34 J·s × 2.0 × 1015 Hz
To simplify the calculation, multiply the numerical parts and then add the indices of 10:
E = (6.63 × 2.0) × (10-34 × 1015)
E = 13.26 × 10-19 J
This can be approximated to 1.33 × 10-18 J. Thus, the energy of light with the given frequency is 1.33 × 10-18 J.
Question 5 Rapport
A medium texture soil with high organic matter is
Détails de la réponse
A medium texture soil with high organic matter is best described as loamy soil. Here's why:
Loamy soil is a type of soil that is characterized by a balanced mixture of sand, silt, and clay particles. Because of this blend, loamy soil is not too coarse like sandy soil, nor is it too compact and dense like clay soil, making it a medium texture.
Moreover, loamy soil is renowned for its high organic matter content. This means that it contains a significant amount of decomposed plant and animal residues, which enrich the soil and provide essential nutrients for plant growth. This high organic content enhances the soil's fertility and structure, enabling it to retain moisture yet drain well, making it ideal for farming and gardening.
In conclusion, due to its balanced texture and richness in organic matter, loamy soil is the best fit for a medium-textured soil with high organic matter.
Question 6 Rapport
The thermometer whose thermometric property is change in volume with temperature is
Détails de la réponse
A thermometer that relies on the **thermometric property** of **change in volume with temperature** is the **Liquid-in-glass thermometer**.
Here is why:
1. **Construction**: A liquid-in-glass thermometer consists of a **glass tube** that encloses a small reservoir filled with a **thermometric liquid**, typically mercury or colored alcohol.
2. **Principle of Operation**: As the **temperature** changes, the **volume of the liquid** inside the tube changes. When the temperature rises, the liquid **expands** and moves up the tube. Conversely, when the temperature decreases, the liquid **contracts** and moves down the tube.
3. **Scale Calibration**: The thermometer has graduations marked along the tube, allowing the user to read the temperature by observing the level of the liquid against these scale markings.
Therefore, the liquid-in-glass thermometer operates on the principle that the **volume of a liquid changes with temperature**, making it the correct answer.
Question 7 Rapport
Find the amount of current required to deposit 0.02kg of metal in a given electrolysis for 120 seconds. [electro chemical equivalent of the metal = 1.3 x 10−7 kgC−1 ]
Détails de la réponse
To determine the amount of current required, we need to use Faraday's laws of electrolysis. The first law states that the mass of the substance deposited at an electrode is directly proportional to the quantity of electricity (or charge) that passes through the electrolyte.
Here, we have:
According to Faraday's first law of electrolysis, the mass (\( m \)) can be calculated by the formula:
m = z \times I \times t
Where:
Rearranging the formula to solve for current \( I \):
I = \(\frac{m}{z \times t}\)
Substituting the given values into the formula:
I = \(\frac{0.02 \, \text{kg}}{1.3 \times 10^{-7} \, \text{kg/C} \times 120 \, \text{s}}\)
Calculating the denominator:
I = \(\frac{0.02}{1.56 \times 10^{-5}}\)
Solving for \( I \):
I = 1282.05 \, \text{A}
Thus, the appropriate amount of current required to deposit 0.02 kg of metal in 120 seconds is approximately 1.3 x 103 A.
Question 8 Rapport
The major building block of an organism is...
Détails de la réponse
The major building block of an organism is Carbon. Let me explain why in a simple yet comprehensive manner:
Carbon is a unique element found in all living organisms. Its importance comes from its ability to form stable bonds with many other elements, including hydrogen, oxygen, nitrogen, phosphorus, and sulfur. This versatility allows carbon to act as a backbone for the building of complex organic molecules, including proteins, nucleic acids (such as DNA and RNA), carbohydrates, and lipids. These molecules are essential for the structure, function, and regulation of the body's tissues and organs.
Here's why Carbon is indispensable:
In summary, Carbon is the primary building block of life due to its unique chemical properties that allow the formation of complex molecules necessary for life's structure and processes.
Question 9 Rapport
In the diagram above, the galvanometer is converted to
Détails de la réponse
To determine what the galvanometer is converted to in the described scenario, let’s first understand how a galvanometer can be transformed into different measuring devices:
1. Galvanometer to Voltmeter: To convert a galvanometer into a voltmeter, a high resistance (known as a multiplier) is connected in series with the galvanometer. This high resistance ensures that the voltmeter can measure a wide range of voltages without drawing significant current from the circuit.
2. Galvanometer to Ammeter: To convert a galvanometer into an ammeter, a low resistance (called a shunt) is connected in parallel with the galvanometer. This allows the majority of the current to pass through the shunt, enabling the ammeter to measure high currents without damaging the galvanometer.
Since the problem statement does not specify any additional details, a general observation is that a galvanometer is commonly converted into an ammeter using a shunt, especially in basic electrical circuits where current measurement is necessary. Therefore, from the options provided, **the galvanometer is most likely converted to an ammeter**.
**In summary**, if a low resistance is added in parallel with the galvanometer, it becomes an ammeter, while adding a high resistance in series would convert it into a voltmeter. Since the context commonly involves conversion for current measurement, the provided diagram likely represents a galvanometer converted into an ammeter.
Question 10 Rapport
Bilateral symmetry,cylindrical bodies and double openings are characteristic features of
Détails de la réponse
Bilateral symmetry, cylindrical bodies, and double openings are characteristic features of nematodes. Nematodes, also known as roundworms, have a body structure that is symmetric along a single plane, which results in two mirror-image halves, thus exhibiting bilateral symmetry.
Furthermore, they usually have a cylindrical body shape, which means their bodies are long and narrow like a cylinder and taper at both ends. This shape helps them move through their environment easily. Additionally, nematodes have a complete digestive system with two openings: a mouth and an anus. This means that food enters through the mouth, gets digested, and waste exits through the anus.
In contrast, organisms like hydra, protozoa, and protists possess different anatomical features. Hydras, for example, typically show radial symmetry, and protozoa and protists generally do not have a well-defined body shape or bilateral symmetry as seen in nematodes. Therefore, the description fits nematodes best.
Question 11 Rapport
The simple form of the lead acid accumulator often has a negative pole of
Détails de la réponse
The simple form of the lead acid accumulator often has a negative pole of lead plate. In a lead-acid battery, the key components include two electrodes and an electrolyte. The **negative pole**, also known as the cathode during discharge, is typically made of **lead (Pb)**, which is in the form of a **lead plate**. When the battery is in use or discharging, this lead reacts with sulphuric acid (the electrolyte) to create lead sulfate.
To break it down further:
Thus, by analyzing the composition and reactions within a lead-acid battery, it is clear that the **negative pole** is made from a **lead plate**.
Question 12 Rapport
A cell of internal resistance of 2Ω supplies current through a resistor, X if the efficiency of the cell is 75%, find the value of X.
Détails de la réponse
To solve the problem, let's first understand the concept of efficiency in this context. Efficiency refers to the ratio of the useful power output to the total power output of a system. In simpler terms, it tells us how much of the power provided by the cell is being effectively used by the resistor, X.
Given that the cell has an internal resistance (r) of 2Ω and we need the efficiency to be 75%, we will follow these steps:
Efficiency (%) = (R / (R + r)) * 100
Where:
According to the problem, efficiency is 75%, so:
(X / (X + 2)) * 100 = 75
First, let’s eliminate the percentage by dividing both sides by 100:
(X / (X + 2)) = 0.75
Now, let's solve for X:
X = 0.75 * (X + 2)
X = 0.75X + 1.5
0.25X = 1.5
X = 1.5 / 0.25
X = 6 Ω
Hence, for the cell to have an efficiency of 75%, the value of the resistor X must be 6Ω.
Question 13 Rapport
The friction due to air mass can be reduced by
Détails de la réponse
Friction due to air mass, also known as air resistance or drag, can be reduced by a concept called **streamlining**.
**Streamlining** refers to the shaping of an object in such a way that it allows air to flow smoothly around it, minimizing turbulence and reducing drag. When air flows smoothly over an object without much disturbance, there is less resistance, and the object can move more easily through the air.
Think of it like how a bullet or a fast-moving car is designed. They have a sleek, smooth shape that cuts through the air with minimal effort. This principle is applied in designing cars, airplanes, and even boats to enhance their efficiency and speed by reducing the friction with the air or water they move through.
Question 14 Rapport
A body is whirled in a horizontal circle at the rate of 800 revolutions per minute. Determine the angular velocity
Détails de la réponse
To determine the angular velocity of a body whirled in a horizontal circle at a rate of 800 revolutions per minute (rpm), we need to convert this to the standard unit of angular velocity, which is radians per second (rad/s).
Here’s how you can calculate it:
Now let's perform the conversion:
Rounding up the decimal to a consistent significant figure, the angular velocity is approximately 26.7π radians per second.
Question 15 Rapport
The web-feet of frogs and toads is basically for
Détails de la réponse
The web-feet of frogs and toads is primarily for swimming. These webbed feet act like paddles, allowing the frog or toad to move efficiently through the water. When the animal spreads its toes, the webbing provides a larger surface area, which gives better propulsion in the water. This adaptation is essential, as many species of frogs and toads spend a significant amount of their time in aquatic environments where efficient swimming helps them in searching for food, escaping predators, and traveling from one place to another. In essence, the webbed feet are a vital feature for their aquatic lifestyle.
Question 16 Rapport
In voltage measurement, the potentiometer is preferred to voltmeter because it
Détails de la réponse
In voltage measurement, a **potentiometer is preferred to a voltmeter** primarily because it **consumes negligible current**. Let me explain this in simpler terms:
A **voltmeter** is an instrument used to measure the potential difference (voltage) across two points in an electrical circuit. However, when a voltmeter is connected, it draws a small amount of current from the circuit to make the measurement, which can slightly alter the voltage being measured. This is particularly an issue in high-resistance circuits where even a small current draw can significantly affect the measurement.
On the other hand, a **potentiometer** is a device designed to measure voltage by comparing it with a known reference voltage without drawing current from the circuit under test. It comes into balance at a point where no current flows through it, ensuring that the measurement is not influenced by the potentiometer itself. This makes it a non-invasive method of measuring voltage, which is particularly useful for precise measurements in sensitive circuits.
Here’s a brief explanation about why the other options listed are less relevant:
Therefore, the key advantage of the potentiometer is its **ability to measure voltage without altering the circuit**, which stems from its negligible current consumption. This **ensures more accurate and reliable measurements** in many applications.
Question 17 Rapport
A practical application of total internal reflection is found in
Détails de la réponse
A practical application of total internal reflection is found in fiber optics.
To understand this, let's break it down:
When light travels from one medium to another (such as from glass to air), it changes direction. This is known as refraction. However, there is a phenomenon called total internal reflection which occurs when light is traveling within a denser medium towards a less dense medium (like from glass to air) and hits the boundary at an angle greater than a certain critical angle. Instead of passing through, the light is completely reflected back into the denser medium.
Fiber optics technology makes use of this principle. In fiber optics, light is transmitted along the core of a thin glass or plastic fiber. The core is surrounded by another layer called the cladding. This cladding has a lower refractive index than the core, which facilitates total internal reflection. As a result, the light continuously reflects internally along the length of the fiber, allowing it to travel long distances with minimal loss.
This property is harnessed in various applications such as in high-speed telecommunication systems, medical equipment like endoscopes, and other technologies that require the transmission of data over long distances with high efficiency.
Question 18 Rapport
The capacitance of a capacitor, C, is inversely proportional to
Détails de la réponse
The capacitance of a capacitor is primarily determined by three key factors: the area of the plates, the distance between the plates, and the dielectric material used between the plates.
Capacitance (C) is calculated using the formula:
\(C = \frac{\varepsilon A}{d}\)
Where:
Let's analyze the relationship:
In summary, the capacitance of a capacitor is inversely proportional to the distance between the plates. Hence, you increase capacitance by decreasing the distance between the plates.
Question 19 Rapport
The dimension of power is
Détails de la réponse
The dimension of power in physics is expressed in terms of the base units of mass (M), length (L), and time (T). Power is the rate at which work is done or energy is transferred over time, and it has the unit of watt (W) which is equivalent to one joule per second.
To derive the dimension of power:
1. Work has the dimension of energy, which is force applied over a distance. The dimension of work (or energy) is M L2 T-2 because force has the dimension M L T-2 and distance adds another L.
2. Since power is work done per unit time, you would divide the dimension of work by time (T).
Thus, the dimensional formula for power is:
M L2 T-3
Question 20 Rapport
Calculate the value of electric field intensity due to a charge of 4μC if the force due to the charge is 8N
Détails de la réponse
To calculate the electric field intensity due to a charge, we need to use the formula:
Electric Field Intensity (E) = Force (F) / Charge (q)
In this problem, we are given that the force (F) is 8 Newtons (N) and the charge (q) is 4 microcoulombs (μC). First, we need to convert the charge from microcoulombs to coulombs:
1 microcoulomb (μC) = 1 x 10-6 coulombs (C)
Therefore, 4 μC = 4 x 10-6 C.
Now we can use the formula to find the electric field intensity:
E = F / q
E = 8 N / (4 x 10-6 C)
E = 8 / 4 x 106
E = 2 x 106
Thus, the value of the electric field intensity is 2 x 106 N/C.
Question 21 Rapport
The diaphragm in the camera is similar to what part of the eyes?
Détails de la réponse
The diaphragm in a camera is similar to the iris in the human eye.
Here's a simple explanation:
In summary, the iris acts like a natural diaphragm, regulating the light that passes through the eye, much like the diaphragm does in a camera.
Question 22 Rapport
An example of a non-rechargeable cell is
Détails de la réponse
A non-rechargeable cell, commonly known as a primary cell, is a type of chemical battery that is designed to be used once until the chemical reactions that produce electricity are exhausted. After this point, the cell cannot be reversed or recharged.
In the given examples, the dry leclanche cell is a well-known example of a non-rechargeable cell. It is commonly used in everyday devices like remote controls, wall clocks, and torches. This cell type utilizes zinc and manganese dioxide as electrodes and relies on a moist paste of ammonium chloride for the electrolyte.
The other examples, such as nickel iron, mercury cadmium, and lead-acid, involve rechargeable cells (secondary cells) that are specifically designed to endure multiple charges and discharges throughout their useful life. Thus, unlike the dry leclanche cell, these can be recharged after use.
Therefore, the dry leclanche cell is an ideal example of a non-rechargeable cell because it can only be used once. After depletion, it cannot be recharged or reused.
Question 23 Rapport
The land and sea breeze is attributed to
Détails de la réponse
The phenomenon of land and sea breeze is primarily attributed to convection.
To understand this, let's first look at what land and sea breezes are:
Land Breeze: At night, the land cools down faster than the sea. The cooler, denser air from the land moves towards the sea, and this is known as a land breeze.
Sea Breeze: During the day, the land heats up more quickly than the sea. The warmer, lighter air over the land rises, and the cooler air from the sea moves in to take its place. This movement of air from the sea to the land is known as a sea breeze.
Both of these processes involve the movement of air due to differences in temperature and density, which is essentially the process of convection.
Convection is the transfer of heat through a fluid (like air or water) and is responsible for moving air masses and creating these breezes. The warm air, being less dense, rises, and the cooler, denser air moves in to replace it.
In contrast, conduction is the transfer of heat through a solid material, and radiation is the transfer of heat in the form of electromagnetic waves, neither of which primarily drive the processes of these breezes, making convection the key player.
Question 24 Rapport
An effort of 40N is applied on a machine to lift a mass of 60kg. Determine the mechanical advantage of the machine [ g = 10ms2 ]
Détails de la réponse
To determine the Mechanical Advantage (MA) of a machine, we use the formula:
MA = Load / Effort
Here, the Load is the weight of the mass being lifted, and the Effort is the force applied on the machine.
First, we need to calculate the Load. The Load is obtained by multiplying the mass of the object by the acceleration due to gravity (g = 10 m/s2).
So, the Load (weight of the mass) is:
Load = Mass × Gravity = 60 kg × 10 m/s2 = 600 N
The Effort given is 40 N.
Now, we can calculate the Mechanical Advantage:
MA = Load / Effort = 600 N / 40 N = 15
Therefore, the Mechanical Advantage of the machine is 15.
Question 25 Rapport
A particular household utilizes three electrical appliances for six hours daily if the appliances are rated 80W, 100W, and 120W respectively. Calculate the electrical bills paid monthly if an average month is 31 days. [1kwh = #24.08k]
Détails de la réponse
To calculate the monthly electrical bill, we first need to determine the total energy consumption of the household in kilowatt-hours (kWh). Here are the steps:
1. Calculate the total power consumption of the appliances daily:
2. Convert the daily power consumption from Watts to kilowatts (kW):
3. Calculate the energy used daily in kWh:
4. Calculate the monthly energy consumption:
5. Calculate the cost based on the rate:
Therefore, the monthly electrical bill is approximately ₦1343.66k.
Question 26 Rapport
A solid cube of aluminum is 1.5cm on each edge. The density of aluminum is 2700kgm−1 . Find the mass of the cube.
Détails de la réponse
The mass of an object can be calculated using the formula:
Mass = Density × Volume
In this case, we need to find the mass of a solid cube of aluminum. Given:
First, we need to calculate the volume of the cube. The volume V of a cube with edge length a is given by:
V = a3
Substitute the edge length:
V = (1.5 cm)3 = 1.5 × 1.5 × 1.5 cm3 = 3.375 cm3
Since the density is given in kg/m3, we should convert the volume from cm3 to m3. There are 1,000,000 cm3 in 1 m3, so:
Volume in m3 = 3.375 cm3 × (1 m3/1,000,000 cm3) = 3.375 × 10-6 m3
Now, use the mass formula:
Mass = Density × Volume
Mass = 2700 kg/m3 × 3.375 × 10-6 m3
This equals:
Mass = 9.1125 × 10-3 kg
Convert kg to grams (since 1 kg = 1000 g):
Mass = 9.1125 grams
So, the mass of the cube is approximately 9.1 g. Thus, the correct answer is 9.1 g.
Question 27 Rapport
The charge of magnitude 1.6 x 10 −19 C is placed in a uniform electric field of intensity 1200Vm−1 . Calculate its acceleration, if the mass of the charge is 9.1 x 10−31 kg
Détails de la réponse
To calculate the acceleration of a charge in an electric field, we start by determining the force acting on the charge. The force \( F \) experienced by a charge \( q \) in a uniform electric field \( E \) is given by the equation:
F = q * E
We are given:
Substituting these values into the equation for force:
F = 1.6 x 10-19 C * 1200 V/m
This results in:
F = 1.92 x 10-16 N
Next, we use Newton’s second law of motion to find the acceleration \( a \) of the charge. This law is given as:
F = m * a
Rearranging for \( a \), we have:
a = F / m
We know:
Substituting these values in the equation for acceleration:
a = \(\frac{1.92 x 10^{-16} N}{9.1 x 10^{-31} kg}\)
Calculating the above expression gives:
a ≈ 2.11 x 1014 ms-2
Therefore, the acceleration of the charge is approximately 2.11 x 1014 ms-2.
Question 28 Rapport
The value of R in the above circuit to make the galvanometer measure 2A is
Détails de la réponse
Given: Ig = 50mA = 0.05A, I to be measured = 2A, r = 2Ω , Is = I - Ig = 2 - 0.05 = 1.95A
Shunt(R) = IgIs x r
R = 0.051.95 x 10 = 0.2564Ω
Question 29 Rapport
Electrolysis can be investigated using
Détails de la réponse
When investigating electrolysis, the most relevant instrument from the list provided is the Voltameter. This is because the voltameter is specifically designed to measure the amount of substance that is deposited or consumed at electrodes during the electrolysis of an electrolyte. It functions based on the chemical change associated with the electric current passing through the electrolyte.
Here is a simple explanation of how electrolysis works and why a voltameter is useful:
Electrolysis is the process of using electricity to cause a chemical reaction, which is usually a decomposition reaction. This involves passing an electric current through an electrolyte (a substance containing free ions). These ions migrate towards electrodes, resulting in chemical changes. The key aspect to measure during electrolysis is the amount of material (e.g., metal or gas) that is deposited at the electrodes.
The Voltameter helps in understanding electrolysis because:
Voltmeter, Ammeter, and Galvanometer are not used primarily for investigating electrolysis:
Question 30 Rapport
A blacksmith heated a metal whose cubic expansivity is 3.9 x 10−6 K−1 . Calculate the area expansivity.
Détails de la réponse
To find the area expansivity of a metal when given its cubic expansivity, you should understand the relationship between linear, area, and cubic expansivity.
Cubic expansivity (\( \beta \)) is defined as the fractional change in volume per change in temperature, and is given by the formula:
\[ \Delta V = \beta V \Delta T \]
Area expansivity (\( \alpha_{A} \)) corresponds to the fractional change in area per change in temperature and can be derived from the linear expansivity (\( \alpha \)). The relationship between these expansivities is as follows:
\[ \text{Area Expansivity (\( \alpha_{A} \))} = 2 \times \text{Linear Expansivity (\( \alpha \))} \]
The cubic expansivity (\( \beta \)) is related to the linear expansivity by:
\[ \text{Cubic Expansivity (\( \beta \))} = 3 \times \text{Linear Expansivity (\( \alpha \))} \]
Thus, based on these relationships, we can express the area expansivity in terms of the cubic expansivity:
\(\text{Area Expansivity (\( \alpha_{A} \))} = \frac{2}{3} \times \text{Cubic Expansivity (\( \beta \))}
Given that the cubic expansivity \( \beta \) is \( 3.9 \times 10^{-6} \, \text{K}^{-1} \):
The area expansivity can be calculated as follows:
\[ \text{Area Expansivity (\( \alpha_{A} \))} = \frac{2}{3} \times 3.9 \times 10^{-6} \, \text{K}^{-1} = 2.6 \times 10^{-6} \, \text{K}^{-1} \]
Therefore, the **correct answer** is **2.6 x 10^{-6} K^{-1}**.
Question 31 Rapport
Find the value of a capacitor with voltage 5V and 30C.
Détails de la réponse
To find the value of the capacitance, we need to use the formula for capacitance:
Capacitance (C) = Charge (Q) / Voltage (V)
In this problem, the charge (Q) is given as 30 Coulombs (C) and the voltage (V) is 5 Volts (V). We can plug these values into the formula:
C = 30 C / 5 V
Calculating the above expression gives:
C = 6 Farads (F)
Therefore, the value of the capacitor is 6 Farads.
Question 32 Rapport
A red shirt under a red light appears pale because red
Détails de la réponse
To understand why a red shirt appears pale under red light, we need to consider how colors are perceived. A shirt's color is due to the light it reflects. A red shirt reflects red light and absorbs other colors. This is why it looks red under normal white light, which is made up of many colors including red.
When you place a red shirt under red light, the only available light to reflect is red. Since the shirt is already designed to reflect red light, it reflects the red light and appears its vivid color. However, it might appear brighter or paler since no other colors are present to contrast against the red.
Therefore, the best explanation is that the red shirt absorbs other colours and reflects red.
Question 33 Rapport
The bursting of water pipes during very cold weather, when the water in the pipes form ice could be attributed to
Détails de la réponse
The bursting of water pipes during very cold weather is primarily attributed to the expansion of water on freezing.
Here's why this happens:
1. **Normal water behavior below freezing:** Typically, when most substances freeze, they contract because the molecules get closer together. However, water behaves differently due to its unique molecular structure. As water freezes, it forms a crystalline structure that makes ice less dense than liquid water, causing it to expand.
2. **Effect of expansion:** When water inside a pipe freezes, it expands. This expansion puts tremendous pressure on the pipe walls because the solid ice takes up more space than the liquid water. Most pipes are rigid and do not have enough room to accommodate the expanded volume of ice.
3. **Resulting pressure:** The increased pressure caused by the expanding ice can cause the pipe to crack or burst, especially if there is no other outlet for the water or ice to expand into.
In summary, pipes burst during cold weather primarily due to the expansion of water as it freezes, which creates pressure that the pipe cannot withstand. This phenomenon is due to the unique property of water where it expands upon freezing, unlike most other substances which contract in their solid form.
Question 34 Rapport
Use the diagram above to answer the question that follows
The zone labelled II is called
Détails de la réponse
The zone labelled II is called the littoral zone.
To explain: The littoral zone is a part of a body of water that is close to the shore. It is typically characterized by abundant sunlight and nutrient availability, making it a highly productive area for aquatic plants and animals. This zone supports various forms of life such as algae, small fish, and invertebrates. The key feature of the littoral zone is its proximity to the shoreline, where sunlight can penetrate to the bottom, allowing for photosynthesis to occur.
Question 35 Rapport
The distance between two successive crests of a water wave is 0.25m. If a particle on the surface of the water makes four complete vertical oscillations in one second. Calculate the speed of the wave.
Détails de la réponse
To calculate the speed of the wave, we need to understand some fundamental wave properties: **wavelength**, **frequency**, and **wave speed**.
1. **Wavelength (\( \lambda \))**: The wavelength is the distance between two successive crests of a wave. In this case, the wavelength is given as **0.25 meters**.
2. **Frequency (\( f \))**: Frequency is the number of complete oscillations or cycles that occur per second. It is given that a particle on the surface of the water makes **four complete vertical oscillations in one second**. So, the frequency is **4 Hz (hertz)**.
3. **Wave Speed (\( v \))**: The speed of a wave is calculated using the formula:
\( v = f \times \lambda \)
Where:
\( v \) is the wave speed,
\( f \) is the frequency, and
\( \lambda \) is the wavelength.
Substitute the given values into the formula:
\( v = 4 \text{ Hz} \times 0.25 \text{ m} \)
\( v = 1 \text{ m/s} \)
Therefore, the **speed of the wave** is 1 m/s.
Question 36 Rapport
Two points on a velocity-time graph have coordinates (2s, 5m/s) and (4s, 15m/s). Calculate the mean acceleration
Détails de la réponse
The mean acceleration of an object is determined by the change in velocity over the change in time. This is given by the formula:
Mean Acceleration (a) = (Final Velocity - Initial Velocity) / (Final Time - Initial Time)
From the velocity-time graph, we have the following points:
Initial Point: (2s, 5m/s)
Final Point: (4s, 15m/s)
Here, the Initial Velocity is 5m/s, the Final Velocity is 15m/s, the Initial Time is 2s, and the Final Time is 4s.
Plug these values into the formula:
Mean Acceleration (a) = (15m/s - 5m/s) / (4s - 2s)
Simplifying this, we get:
Mean Acceleration (a) = 10m/s / 2s = 5m/s²
The mean acceleration is therefore 5.0 m/s².
Question 37 Rapport
I It wets glass
II It needs to be coloured
III It has a low density
Water is not suitable for use as a thermometric liquid because
Détails de la réponse
Water is not suitable for use as a thermometric liquid because:
a) It wets glass: This can cause issues with reading the level of the liquid.
b) It needs to be coloured: Water is typically clear, making it difficult to see the level without coloring.
c) It has a low density: This can affect the sensitivity and accuracy of the thermometer.
Question 38 Rapport
An air force jet flying with a speed of 335m/s went past an anti-aircraft gun. How far is the aircraft 5s later when the gun was fired?
Détails de la réponse
To solve this problem, we need to determine how far the aircraft travels in the 5 seconds after it passes the anti-aircraft gun. The problem gives us two key pieces of information:
To find the distance traveled, we use the formula for distance:
Distance = Speed × Time
Plugging in the given values:
Distance = 335 m/s × 5 s
Calculating this, we get:
Distance = 1675 meters
This means the aircraft is 1675 meters away from the point where it passed the anti-aircraft gun after 5 seconds.
Question 39 Rapport
Pilots uses aneroid barometer to know the height above sea level because
Détails de la réponse
Aneroid barometers are compact and lightweight, making them suitable for use in aircraft where space and weight are critical considerations. They provide a reliable measurement of altitude based on changes in atmospheric pressure.
Question 40 Rapport
A sonometer's fundamental note is 50Hz, what is the new frequency when the tension is four times the original?
Détails de la réponse
To solve this problem, we need to understand the relationship between tension and frequency in a sonometer wire. The frequency of a vibrating string, such as one in a sonometer, is directly proportional to the square root of the tension in the string. Mathematically, this relationship is expressed as:
f ∝ √T
Where f is the frequency and T is the tension. In the given problem, the original frequency is 50 Hz, and the tension is increased to four times its original value. Let's analyze how this change in tension affects the frequency:
- Original tension = T
- New tension = 4T
Substitute the new tension into the formula:
f_new = 50 Hz × √(4T/T)
Simplify the equation:
f_new = 50 Hz × √4
f_new = 50 Hz × 2
f_new = 100 Hz
Thus, when the tension is four times the original tension, the new frequency of the sonometer's fundamental note becomes 100 Hz.
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