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A wooden packaging box of dimension 30 cm by 50 cm by 85 cm has a mass of 70 ke. Determine the: (1) maximum pressure; (ii) minimum pressure it can exert on a horizontal surface. (5 marks)craft1 electrical June/July 2020
i. To find the maximum pressure, we can assume that the weight of the box is evenly distributed across the entire bottom surface of the box. In that case, the pressure on the bottom surface would be equal to the weight of the box divided by the area of the bottom surface. The area of the bottom surfRead more
i. To find the maximum pressure, we can assume that the weight of the box is evenly distributed across the entire bottom surface of the box. In that case, the pressure on the bottom surface would be equal to the weight of the box divided by the area of the bottom surface. The area of the bottom surface is 30 cm * 50 cm = 1500 sq cm, so the maximum pressure would be 70,000 g / 1500 sq cm = 46.67 g/sq cm.
ii. To find the minimum pressure, we can assume that all of the weight of the box is concentrated in a single point at the bottom center of the box. In that case, the pressure on the bottom surface would be equal to the weight of the box divided by the area of a small circle with a radius equal to the distance from the center of the box to any of the corners. The distance from the center of the box to a corner is (85 cm / 2) * sqrt(2) = 59.5 cm, so the radius of the circle would be 59.5 cm / 2 = 29.75 cm. The area of this circle is 29.75 cm * 29.75 cm * pi = 2744.63 sq cm, so the minimum pressure would be 70,000 g / 2744.63 sq cm = 25.47 g/sq cm.
See lessA technician at a battery manufacturing plant has a liquid bottle labelled “inorganic. acid”. Outline four chemical methods used to verify the properties of the liquid. (4 marks)craft1 electrical June/July 2020
Density measurement: The density of a liquid can be measured using a hydrometer or a digital density meter. This can help to confirm the identity of the liquid, as different inorganic acids have different densities. pH measurement: The pH of a liquid can be measured using a pH meter or pH paper. InoRead more
A fluorescent lamp tube is filled with a gas containing a mixture of mercury vapour and an inert gas. The gas pressure is 304Pa at 23°C. Determine the gas pressure at 95°C. (4 marks)craft1 electrical June/July 2020
To determine the gas pressure at 95°C, we can use the ideal gas law: PV = nRT where P is the pressure of the gas, V is the volume of the gas, n is the number of moles of gas, R is the ideal gas constant, and T is the temperature of the gas in kelvin. Since the volume and number of moles of gas are cRead more
To determine the gas pressure at 95°C, we can use the ideal gas law:
PV = nRT
where P is the pressure of the gas, V is the volume of the gas, n is the number of moles of gas, R is the ideal gas constant, and T is the temperature of the gas in kelvin.
Since the volume and number of moles of gas are constant, we can rearrange the formula to solve for P:
P = (nRT) / V
We can substitute the given values into the formula to solve for the gas pressure at 95°C:
P = (n * R * (95°C + 273)) / V = (n * R * 368) / V = (304Pa * 368) / V = 112,192 Pa / V
Since the volume of the gas is constant, the pressure of the gas at 95°C will be proportional to the pressure at 23°C. Therefore, the gas pressure at 95°C will be 112,192 Pa / 304 Pa = 368 times the gas pressure at 23°C.
The gas pressure at 95°C is 368 * 304 Pa = 112,192 Pa.
See lessState Fleming’s right hand rule for electric generators. (3 marks)craft1 electrical June/July 2020
Fleming's right hand rule for electric generators states that if the thumb, forefinger, and middle finger of the right hand are extended and mutually perpendicular, with the forefinger pointing in the direction of the magnetic field and the thumb pointing in the direction of motion of the conductor,Read more
Fleming’s right hand rule for electric generators states that if the thumb, forefinger, and middle finger of the right hand are extended and mutually perpendicular, with the forefinger pointing in the direction of the magnetic field and the thumb pointing in the direction of motion of the conductor, the middle finger will point in the direction of the induced current.
See lessAn inclined plane has a velocity ratio of 2 and efficiency of 95%. It is used to raise a load of 400 N. Determine the: i. mechanical advantage; ii. effort required. (4 marks)craft1 electrical June/July 2020
i. To solve this problem, we can use the formulas for mechanical advantage and efficiency: Mechanical advantage = Output force / Input force Efficiency = (Output work) / (Input work) First, we can use the given velocity ratio to calculate the mechanical advantage: Mechanical advantage = (Output distRead more
i. To solve this problem, we can use the formulas for mechanical advantage and efficiency:
Mechanical advantage = Output force / Input force
Efficiency = (Output work) / (Input work)
First, we can use the given velocity ratio to calculate the mechanical advantage:
Mechanical advantage = (Output distance) / (Input distance) = 2
Since the mechanical advantage is equal to the velocity ratio, we can conclude that the output distance is twice the input distance.
ii. Next, we can use the given efficiency to calculate the input work:
Input work = Output work / Efficiency = (Output force * Output distance) / Efficiency
Substituting the values given in the problem, we get:
Input work = (400 N * Output distance) / 0.95
Since the output distance is twice the input distance, we can substitute 2 * Input distance for Output distance:
Input work = (400 N * 2 * Input distance) / 0.95
Solving for the input distance, we get:
Input distance = Input work / (400 N * 2 / 0.95) = 509.2 m
The input distance is equal to the input force applied to the inclined plane, so the input force is 509.2 N.
To calculate the effort required, we can use the formula for mechanical advantage:
Effort = Load / Mechanical advantage = 400 N / 2 = 200 N
The effort required to raise the load is 200 N.
See less(i) Define each of the following as used in simple machine: i. mechanical advantage; ii. velocity ration; iii. efficiency.(3 marks)craft1 electrical June/July 2020
(i) Mechanical advantage: Mechanical advantage is the ratio of the force applied to a simple machine to the force output by the machine. It is a measure of how much the machine amplifies the force applied to it. (ii) Velocity ratio: Velocity ratio is the ratio of the distance traveled by the input fRead more
(i) Mechanical advantage: Mechanical advantage is the ratio of the force applied to a simple machine to the force output by the machine. It is a measure of how much the machine amplifies the force applied to it.
(ii) Velocity ratio: Velocity ratio is the ratio of the distance traveled by the input force to the distance traveled by the output force in a simple machine. It is a measure of how much the machine increases or decreases the speed of the input force.
(iii) Efficiency: Efficiency is the ratio of the work output by a simple machine to the work input to the machine. It is a measure of how much of the input work is converted into useful output work, with the remainder being lost to friction and other sources of energy loss.
See lessAn industrial electric boiler rated at 4 kW contains 612 kg of water at 80°C. To adjust boiler level to safe value, 78 kg of water at 26°C was added. Determine the: (i) new temperature of water in the boiler; (ii) time required to restore water temperature to 80°C. (7 marks)craft1 electrical June/July 2020
i. To solve this problem, we can use the formula for the specific heat capacity of water: c = Q / (m * ΔT) where c is the specific heat capacity of water, Q is the heat added to the water, m is the mass of the water, and ΔT is the change in temperature. We can rearrange this formula to solve for Q:Read more
i. To solve this problem, we can use the formula for the specific heat capacity of water:
c = Q / (m * ΔT)
where c is the specific heat capacity of water, Q is the heat added to the water, m is the mass of the water, and ΔT is the change in temperature.
We can rearrange this formula to solve for Q:
Q = c * m * ΔT
First, we need to calculate the heat added to the water when it was added to the boiler. We can do this by using the specific heat capacity of water, which is 4.186 J/g°C:
Q = 4.186 J/g°C * 78 kg * (80°C – 26°C) = 214,054 J
Next, we need to calculate the new temperature of the water in the boiler. We can do this by using the formula for the heat capacity of a substance, which is given by:
C = Q / ΔT
where C is the heat capacity of the substance, Q is the heat added to the substance, and ΔT is the change in temperature.
We can rearrange this formula to solve for ΔT:
ΔT = Q / C
The heat capacity of the water in the boiler is given by:
C = c * m = 4.186 J/g°C * (612 kg + 78 kg) = 3,003,108 J/°C
Substituting these values into the formula for ΔT, we get:
ΔT = 214,054 J / 3,003,108 J/°C = 0.07°C
The new temperature of the water in the boiler is 80°C + 0.07°C = 80.07°C
ii. Finally, we need to calculate the time required to restore the water temperature to 80°C. We can do this by using the formula:
t = Q / (P * η)
where t is the time required, Q is the heat added to the water, P is the power of the heating element, and η is the efficiency of the heating element.
Since the boiler is rated at 4 kW, the power of the heating element is 4 kW. The efficiency of the heating element is not given, so we will assume it is 100% efficient (η = 1).
Substituting these values into the formula, we get:
t = 214,054 J / (4 kW * 1) = 53,513 s
The time required to restore the water temperature to 80°C is approximately 53,513 seconds, or about 14.9 hours.
See lesstwo methods of reducing effect of noise to a person in a poisy workshop. (2 marks)craft1 electrical June/July 2020
Sound-absorbing materials: Installing sound-absorbing materials, such as foam panels or carpet, can help to reduce the level of noise in the workshop by absorbing sound waves. Noise-cancelling headphones: Wearing noise-cancelling headphones can help to reduce the level of noise that a person is expoRead more
one application of polarized light in electronics.(1 marks)craft1 electrical June/July 2020
Display screens: Polarized light can be used in display screens, such as LCD screens, to reduce glare and improve the visibility of the screen in bright environments. Optical fibers: Polarized light can be used to transmit data through optical fibers, which are thin strands of glass or plastic thatRead more