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Question 1 Report
One of these is not the use of an electroscope
Answer Details
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 Report
Convert 60ºC to degree Fahrenheit
Answer Details
To convert temperatures from Celsius to Fahrenheit, we use the formula:
F = (C × 9/5) + 32
Here, F represents the temperature in Fahrenheit, and C represents the temperature in Celsius.
Let's use this formula to convert 60ºC to Fahrenheit:
F = (60 × 9/5) + 32
First, multiply 60 by 9/5:
60 × 9/5 = 108
Next, add 32 to 108:
108 + 32 = 140
Therefore, 60ºC is equal to 140ºF.
Question 3 Report
The part of the inner ear that is responsible for hearing is
Answer Details
The part of the inner ear that is responsible for hearing is the cochlea.
The inner ear is a complex structure, and each of its components serves different functions. Let me break it down further:
Thus, the cochlea is the crucial component of the inner ear responsible for converting sound vibrations into nerve signals, making it central to the process of hearing.
Question 4 Report
Two points on a velocity-time graph have coordinates (2s, 5m/s) and (4s, 15m/s). Calculate the mean acceleration
Answer Details
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 5 Report
In electrolysis, when same quantity of electricity is passed through different electrolytes, mass of substances deposited is proportional to
Answer Details
In electrolysis, when the same quantity of electricity is passed through different electrolytes, the mass of substances deposited is proportional to their chemical equivalent. The reason for this lies in Faraday's laws of electrolysis. Faraday's second law states that the amounts of different substances deposited or liberated by the same quantity of electricity are proportional to their chemical equivalents.
Chemical equivalent refers to a measure of a substance's ability to react or be deposited during electrolysis, and it is calculated as the molar mass divided by valency (n). This is why it is sometimes also referred to as equivalent weight.
In essence, for a given charge (equal number of electrons or electricity), a substance with a lower chemical equivalent will deposit more mass because it requires fewer electrons to undergo the chemical change.
Question 6 Report
The energy in a moving car is an example of
Answer Details
The energy in a moving car is an example of kinetic energy.
To explain simply, **energy** is the ability to do **work** or cause **change**. There are different forms of energy, and **kinetic energy** is one of them. It is defined as the energy possessed by an object due to its motion.
When a car is moving, it possesses **kinetic energy** because its components are in **motion**. This motion energy allows the car to do tasks, such as transporting people or goods from one place to another. The faster the car moves, the greater its **kinetic energy**, and thus it can make a larger impact or do more work.
In contrast, energy forms like **mechanical energy** is a combination of both kinetic and potential energy; **electrical energy** is associated with electrical charge movement, while **potential energy** is related to the position or condition of an object (like a car parked on a hill). Therefore, the specific type of energy from a moving car is **kinetic energy**.
Question 7 Report
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
Answer Details
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 8 Report
The friction due to air mass can be reduced by
Answer Details
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 9 Report
What is the inductance reactance of a coil of 7H when connected to a 50Hz a.c circuit?
Answer Details
To determine the inductive reactance of a coil, we use the formula:
Inductive Reactance (XL) = 2πfL
Where:
Given:
Substituting the given values into the formula:
XL = 2 × π × 50 × 7
Calculating this:
XL = 2 × 3.14159 × 50 × 7
XL ≈ 2 × 3.14159 × 350
XL ≈ 2 × 1099.557
XL ≈ 2199.114
Therefore, the inductive reactance of the coil is approximately 2200Ω.
Question 10 Report
A practical application of total internal reflection is found in
Answer Details
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 11 Report
The energy stored in the above capacitor is
Answer Details
The energy stored in the capacitor = 12 q2C
Where C = 2F, q = 3C
= 12 322 = 94 = 2.25J
Question 12 Report
Calculate the upthrust on a spherical ball of volume 4.2 x 10−4 m3 when totally immersed in a liquid of density 1028kgm−3
Answer Details
Upthrust(Force) = volume of object x density of liquid x g = V x ρ x g
U = 4.2 x 10−4 x 1028 x 10 ≊ 4.3N
Question 13 Report
The value of R required to make the galvanometer measure voltage up to 40V in the diagram above
Answer Details
In a galvanometer setup intended to measure voltages, you often encounter a configuration known as a voltmeter, where a resistor is added in series with the galvanometer to increase its range of measurement.
The basic principle is that the total resistance of the voltmeter (comprising the galvanometer's resistance and the additional series resistor) allows it to handle a higher voltage by limiting the current that flows through the galvanometer. The maximum voltage (V) that can be measured by the galvanometer is determined by Ohm's Law: V = I * R,
Where:
Assuming the galvanometer has a known internal resistance (G) and a known full-scale current (I_fullscale), the resistance R required in series can be calculated via the formula:
R = (V / I_fullscale) - G
For this solution, you need either the values of G and I_fullscale or their product (G * I_fullscale). Without those exact specifications provided, it would be imprudent to give an exact numeric answer.
However, if this is a typical example and you have a typical galvanometer with a full-scale current of 50 μA and an internal resistance of 500 Ω, you can compute:
R = (40 / 50 x 10^-6) - 500 = 2000 - 500 = 1500 Ω
Therefore, you would need an additional R = 1990 Ω - 1500 Ω = 490 Ω, meaning the closest possible practical value from your choices is 1990 Ω (including the internal resistance).
If the specific parameters of the galvanometer differ, adjust the calculation accordingly, but the general process is as laid out here.
Question 14 Report
Photometer is used to measure
Answer Details
A photometer is an instrument designed to measure the intensity of light. It is used to determine how much light is received over a particular area. Photometers are vital in various fields such as photography, astronomy, and laboratory science for ensuring that light levels are appropriate for specific applications.
The device operates by assessing the brightness or illumination coming from a light source and comparing it with a standard light. The measurement can be displayed in different units such as lumens or lux, depending on the context of the measurement.
While photometers are focused on the intensity of light, they do not measure kinetic energy of liberated electrons, the frequency of light, or the wavelength of light. These quantities are measured using other specialized instruments, such as spectrometers or frequency analyzers.
Question 15 Report
The diaphragm in the camera is similar to what part of the eyes?
Answer Details
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 16 Report
A light ray passing from air into water at an angle of 30º from the normal in air would
Answer Details
When light passes from one medium to another, such as from air to water, it bends or refracts. This phenomenon is described by Snell's Law, which states: n₁ * sin(θ₁) = n₂ * sin(θ₂), where:
The refractive index of air is approximately 1, and the refractive index of water is approximately 1.33. Given the angle of incidence in air is 30º:
Using Snell's Law:
1 * sin(30º) = 1.33 * sin(θ₂)
You will find:
sin(θ₂) = sin(30º) / 1.33
sin(θ₂) ≈ 0.5 / 1.33
sin(θ₂) ≈ 0.375
Now, solve for θ₂ by taking the inverse sine (arcsin):
θ₂ ≈ arcsin(0.375)
θ₂ ≈ 22.09º
Thus, when a light ray passes from air into water at an angle of 30º from the normal in air, it will make an angle less than 30º from the normal in water, approximately 22.09º. This is because the light ray bends toward the normal as it enters a denser medium (water).
Question 17 Report
The dimension of power is
Answer Details
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 18 Report
The mechanical advantage of the machine shown above
Answer Details
Mechanical advantage of a machine = LOADEFFORT
In this case of a wedge, we can consider the dimensions given:
Load distance (height of the machine): 15 cm
Effort distance (movement of the effort): 0.5 cm
M.A = 150.5 = 30.0
Question 19 Report
Calculate the quantity of heat for copper rod whose thermal capacity is 400Jk−1 for a temperature change of 60ºC to 80ºC
Answer Details
To calculate the quantity of heat absorbed or released by a substance, we can use the formula:
Q = C × ΔT
where:
Given:
First, calculate the change in temperature:
ΔT = Final temperature - Initial temperature = 80°C - 60°C = 20°C
Now, substitute the values into the formula to find the quantity of heat:
Q = 400 J/°C × 20°C
Calculate the answer:
Q = 8000 J
Since the options provided are in kilojoules (KJ), we need to convert joules (J) to kilojoules (1 KJ = 1000 J):
Q = 8000 J ÷ 1000 = 8 KJ
Therefore, the quantity of heat for the copper rod, given the specified conditions, is 8 KJ.
Question 20 Report
The changes of living organisms over generation is referred to as
Answer Details
The changes of living organisms over generations are referred to as organic evolution.
Organic evolution, also known as biological evolution, is the process through which species of organisms undergo changes over time due to genetic variations and environmental factors. This leads to the development of new traits and, over long periods, may result in the emergence of new species.
Here's a simple breakdown of the concept:
This process is a key concept in biology and is fundamental to understanding the diversity of life on Earth. Organic evolution is distinct from other kinds of evolution mentioned, as it specifically deals with biological organisms.
Question 21 Report
Infra-red thermometers work by detecting the
Answer Details
Infra-red thermometers work by detecting the radiation from the body and converting it to temperature. These thermometers are designed to measure the infrared radiation, also known as heat radiation, emitted by objects. All objects with a temperature above absolute zero emit infrared radiation. The thermometer's sensor captures this radiation and converts it into an electrical signal that can be read as a temperature measurement. This method allows for quick, non-contact temperature readings, which is why infrared thermometers are often used in medical settings, industrial applications, and more.
Question 22 Report
Mouth part adapted for piercing and sucking is found in
Answer Details
The mouthpart adapted for piercing and sucking is found in the mosquito. Mosquitoes have a specialized mouth structure called a proboscis. This proboscis is long and slender, allowing mosquitoes to puncture the skin of their hosts and suck blood. The proboscis is a complex structure that contains several needle-like parts that make the piercing and sucking process efficient and effective.
Question 23 Report
Calculate the depth of a swimming pool if the apparent depth is 10cm. ( Refractive index of water = 1.33 )
Answer Details
To calculate the real depth of a swimming pool given the apparent depth, we can use the concept of refraction of light. When light passes from one medium to a denser medium, it bends towards the normal. This bending effect causes objects submerged in water to appear closer to the surface than they actually are. The formula to relate these depths is given by:
Real Depth = Apparent Depth × Refractive Index
Given the problem:
Using the formula:
Real Depth = 10 cm × 1.33
Calculating the above:
Therefore, the depth of the swimming pool is 13.3cm.
Question 24 Report
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
Answer Details
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 25 Report
The average translational kinetic energy of gas molecules depends on
Answer Details
The average translational kinetic energy of gas molecules is directly related to the temperature of the gas. This relationship is based on the principles of kinetic molecular theory, which explains the behavior of gas molecules in terms of their motion.
Let's break this down simply:
1. Temperature and Kinetic Energy:
The average translational kinetic energy of gas molecules is given by the equation:
\( KE_{avg} = \frac{3}{2} k_B T \)
where \( KE_{avg} \) is the average translational kinetic energy, \( k_B \) is the Boltzmann constant, and \( T \) is the absolute temperature in Kelvin. This formula shows that the kinetic energy is directly proportional to the temperature.
2. What This Means:
As the temperature of a gas increases, the molecules move faster, which increases their translational kinetic energy. Conversely, as the temperature decreases, the molecules slow down, resulting in lower kinetic energy.
It is important to note that this relation is independent of the pressure and the number of moles of the gas. While pressure and the number of moles do affect the overall behavior of a gas, they do not directly influence the average translational kinetic energy of individual molecules.
Therefore, the correct explanation is that the average translational kinetic energy of gas molecules depends on temperature only.
Question 26 Report
The gravitational force between two objects masses 1024 kg and 1027 kg is 6.67N. Calculate the distance between them [ G = 6.6 x 10−11 Nm2 kg−2 ]
Answer Details
To calculate the distance between two objects based on the gravitational force acting between them, we need to use the formula for gravitational force:
F = (G * m1 * m2) / r²
Where:
We need to compute r by rearranging the formula:
r² = (G * m1 * m2) / F
Therefore, the distance r is:
r = √((G * m1 * m2) / F)
Substitute the given values into the equation:
r = √((6.6 x 10-11 Nm²/kg² * 1024 kg * 1027 kg) / 6.67 N)
Calculating inside the square root:
G * m1 * m2 = 6.6 x 10-11 * 1024 * 1027 = 6.6 x 1040 Nm²
Then divide by the force:
6.6 x 1040 Nm² / 6.67 N = 0.99 x 1040 m²
Finally, calculate the square root:
r = √(0.99 x 1040)
r ≈ 1.0 x 1020 m
Therefore, the distance between the two objects is approximately 1.0 x 1020 m.
Question 27 Report
A sonometer's fundamental note is 50Hz, what is the new frequency when the tension is four times the original?
Answer Details
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.
Question 28 Report
The degree of precision of a vernier caliper is
Answer Details
The degree of precision of a vernier caliper is actually the **smallest value** that the vernier scale can measure, which can be considered as the resolution or least count of the instrument. The degree of precision for most standard vernier calipers is 0.01 cm (or 0.1 mm). This means that the caliper can measure dimensions down to a hundredth of a centimeter.
To understand why this is the case, consider the construction of a vernier caliper:
This alignment allows more precise measurements than the main scale alone. If the vernier scale has 10 divisions which coincide over a length equal to 9 divisions on the main scale, then each division of the vernier scale represents an extra 0.01 cm. Therefore, it allows measuring smaller intervals between the main scale markings very precisely.
Thus, you won't find vernier calipers with a degree of precision of 0.005 cm, 0.1 cm, or 1.0 cm as options in standard practice for precise measurement tools.
Question 29 Report
An ideal transformer has
Answer Details
An ideal transformer is a hypothetical concept used in electrical engineering to simplify the analysis of real transformers. In an ideal transformer, several assumptions are made to avoid losses and inefficiencies. Here's what an ideal transformer has:
No flux leakage: In an ideal transformer, it is assumed that all the magnetic flux generated in the primary coil is perfectly linked with the secondary coil. This means there is no flux leakage. This assumption ensures maximum efficiency, as all the energy is transferred from the primary to the secondary coil without losses.
Let's briefly discuss the other concepts to understand why they don't pertain to an ideal transformer:
Maximum primary resistance: In an ideal transformer, the resistance of the windings is assumed to be zero. If the primary has maximum resistance, it would result in power loss due to the resistance, contradicting the idea of an ideal transformer.
Hysteresis: This refers to the energy loss that happens in the core material due to the cyclic magnetization and demagnetization processes. An ideal transformer assumes there is no hysteresis loss, meaning the core material does not absorb any energy during these cycles.
Eddy current: These are loops of electric current induced within conductors by a changing magnetic field, which can cause significant energy loss. In an ideal transformer, it is assumed that there are no eddy currents, hence no energy loss due to this effect.
In summary, an ideal transformer is characterized by having no flux leakage, and it assumes that there are no losses due to resistance, hysteresis, or eddy currents. This makes the ideal transformer a perfect, lossless device for the purposes of theoretical analysis.
Question 30 Report
The moon's acceleration due to gravity is 16 of the earth's value. The weight of a bowling ball on the moon would be
Answer Details
To determine the weight of a bowling ball on the moon, we need to understand the relationship between weight, gravity, and mass.
Weight is the force exerted by gravity on an object. On Earth, this force depends on the object's mass and the acceleration due to gravity, which is approximately 9.8 m/s². Weight can be calculated using the formula:
Weight = Mass x Gravity
On the moon, the acceleration due to gravity is only 1/6 of Earth’s gravity. This means the gravitational pull on the moon is much weaker compared to the Earth. If we take the Earth's gravity to be 9.8 m/s², the moon's gravity would be:
Moon's Gravity = (9.8 m/s²) x (1/6) ≈ 1.63 m/s²
Given that the weight of an object is directly proportional to the gravitational force, the weight of an object on the moon would be substantially less than its weight on Earth. Thus, the weight of the bowling ball on the moon would be:
Weight on Moon = (Mass) x (1.63 m/s²) = 1/6 of its weight on Earth
Therefore, the weight of a bowling ball on the moon is 1/6 of its weight on Earth.
Question 31 Report
Answer Details
To solve this problem, we need to understand the relationship between pressure, volume, and temperature of a gas. The relevant law here is the **Combined Gas Law**, which is expressed as:
(P1 * V1) / T1 = (P2 * V2) / T2
Where:
In the given problem:
Applying the Combined Gas Law:
(P1 * V1) / 300 = (2 * P1 * V2) / 400
Simplifying this equation:
V1/300 = 2V2/400
Multiply both sides by 400 to clear the fraction:
400 * V1 / 300 = 2 * V2
Which further simplifies to:
(4/3) * V1 = 2 * V2
Dividing both sides by 2:
(2/3) * V1 = V2
This shows that the final volume, V2, is **2/3 of the initial volume, V1**. Therefore, the volume of the gas will **decrease by 1/3**.
Question 32 Report
Under which conditions is work done
Answer Details
In physics, the concept of work is defined as the process of energy transfer that occurs when a force makes an object move. The conditions for work to be done are:
Now, let's evaluate each scenario:
A man supports a heavy load on his head with hands: In this case, although the man is applying a force upward to support the load, the load does not move in the direction of the force he is exerting (upward). Hence, no work is done.
A woman holds a pot of water: Similar to the first scenario, the woman applies an upward force to hold the pot. However, the pot remains stationary, and there is no movement in the direction of the force. Thus, no work is done.
A boy climbs onto a table: Here, as the boy climbs, he applies a force to move himself upward onto the table. The movement is in the direction of the upward force he is applying. Therefore, work is done.
A man pushes against a stationary petrol tanker: In this scenario, although the man is applying a force to the tanker, it does not move. Because there is no movement in the direction of the force, no work is done.
Question 33 Report
When a cell of e.m.f 3.06V is connected, the balance of a potentiometer is 75cm, Calculate the new balance of a cell of e.m.f 2.295V
Answer Details
To solve this problem, we first need to understand the principle behind a potentiometer. A potentiometer is a device used to measure the electromotive force (e.m.f) of a cell by comparing it with a known voltage. The balance length on a potentiometer corresponds to a proportional measurement of the e.m.f.
Let's denote:
- \( V_1 \): the e.m.f of the first cell = 3.06V
- \( l_1 \): the balance length for the first cell = 75 cm
- \( V_2 \): the e.m.f of the second cell = 2.295V
- \( l_2 \): the balance length for the second cell (which we need to find)
The basic relationship for a potentiometer is given by:
\( V_1 / V_2 = l_1 / l_2 \)
Substituting the given values:
\( 3.06 / 2.295 = 75 / l_2 \)
We need to solve for \( l_2 \):
\( l_2 = (2.295 \times 75) / 3.06 \)
Now, calculating the above expression:
\( l_2 = 171.975 / 3.06 \approx 56.26 \) cm
Therefore, the new balance length for the cell with an e.m.f of 2.295V is approximately 56.26 cm.
Question 34 Report
Find the value of a capacitor with voltage 5V and 30C.
Answer Details
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 35 Report
The bursting of water pipes during very cold weather, when the water in the pipes form ice could be attributed to
Answer Details
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 36 Report
Electrolysis can be investigated using
Answer Details
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 37 Report
A rectifier is a device that changes
Answer Details
A rectifier is a device that changes alternating current (A.C) to direct current (D.C). Alternating current is the type of electrical current that changes direction periodically, while direct current flows in a single, constant direction.
Rectifiers are essential in numerous electrical devices, particularly those that require a stable and consistent power supply. For example, most electronic devices like mobile phone chargers, laptop adapters, and televisions operate on D.C. power, and rectifiers convert the household A.C. power supply to D.C. so that these devices can function properly.
In summary, a rectifier converts A.C., which is alternating power supply, into D.C., which is a steady flow of electricity in one direction, making it usable for electronic devices and various applications that require direct current.
Question 38 Report
At absolute zero temperature, the average velocity of the molecules
Answer Details
At absolute zero temperature, which is defined as 0 Kelvin or -273.15 degrees Celsius, the energy of molecular motion ceases. This means that the molecules theoretically have minimal energy, and hence, their motion stops entirely. Therefore, the average velocity of the molecules is zero. In reality, absolute zero is a theoretical limit, and it is practically unreachable, but it serves as a concept to help in understanding the behavior of molecules at extremely low temperatures. Thus, under this theoretical condition, the average motion of molecules would be nonexistent. In summary, the average velocity of the molecules at absolute zero is zero.
Question 39 Report
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.
Answer Details
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 40 Report
What will be the weight of a man of mass 60kg standing in a lift if the lift is descending vertically at 3ms2 ?
Answer Details
To find the apparent weight of a man of mass 60 kg standing in a descending lift, we first need to understand the concept of apparent weight. Apparent weight is the force that the man feels as his weight due to the reaction of the lift floor on him. When the lift accelerates, the apparent weight changes from his actual weight.
In this case, the lift is descending with a constant velocity of 3 m/s2. Since the acceleration is downward, it means the lift is accelerating negatively compared to an upward acceleration.
The formula to find the apparent weight (Wapparent) when in a lift is:
Wapparent = m(g - a)
Where:
Substituting these values into the formula, we get:
Wapparent = 60 (9.8 - 3)
Calculating further:
Wapparent = 60 × 6.8
Wapparent = 408 N
The closest option to 408 N in the answers provided is 420 N. Therefore, the correct answer is 420 N.
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