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Mechanics
Thermal Physics
Waves
Electricity & Magnetism
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100
Give the physical quantity that has the same unit as energy.
moment of a force
100
Define the term "latent heat of vaporisation".
The thermal energy that converts an object from the liquid state to gaseous state at constant temperature.
100
Name a component of the EM spectrum has a wavelength shorter than microwaves but has a frequency smaller than red light.
infra-red rays
100
Calculate the effective resistance of ten 1.0ohm and ten 2.0ohm resistors in parallel.
[ (10 x 1) + (10 x 0.5)]^-1 = [10 + 5]^-1 =0.067ohm
100
What is the unit of resistivity?
ohm.m
200
An object is released from rest from a hot air balloon. The object eventually reaches terminal velocity. Describe the speed of the object.
first part: The speed increases at a decreasing rate (decreasing acceleration). second part: The speed is constant.
200
What is the temperature of 25 deg C in SI unit?
298.15K
200
A converging lens has a focal length of 8.0cm. Describe the image when the object is moved from 17.0cm to 9.0cm away from the lens.
17.0cm to more than 16.0cm: inverted, real and diminished 16.0cm: inverted, real and same size less than 16.0cm to 9.0cm: inverted, read and enlarged
200
State and explain why the core of transformer is laminated.
To prevent power loss due to Eddy current. In prevents the set up of induced current in the core that opposes the change of the magnetic field that induces it.
200
Name two similarities between ultrasound and ultraviolet rays.
They obeys the Law of Refraction. They obeys the Law of Reflection. They transfer energy without the bulk movement of the medium.
300
Explain why oil is used in hydraulic system instead of gas and water?
Cannot be compressed and thus pressure can be transmitted uniformly in the hydraulic system. Oil can lubricate the components, does not promote rusting of the metal parts OR have a higher boiling point than water.
300
An electrical heater is placed at the bottom of a pot of water. Some potatoes are floating on the water. State how thermal energy is used to cook the potatoes.
Conduction from heater to water particles next to the heater. Convection in the water. Conduction from the hot water particles at the surface to the potatoes.
300
A wave has the following properties: amplitude = 2.5cm; frequency = 4.0Hz; wavelength = 10.0cm. Calculate the time it takes for a wave particle to travel 50.0cm.
distance of one oscillation = 2.5cm x 4 = 10.0cm no. of oscillation in 50.0cm = 5 time to complete one oscillation = 1/4.0 = 0.25s time taken = 5 x 0.25s = 1.25s
300
Explain why an uncharged ping pong ball is attracted to a charged sphere.
The charged sphere induces an opposite charge on the surface of the ping pong ball nearest to it. Since the attractive force of the opposite charges is greater than the repulsion of the like charges, the ping pong ball is attracted.
300
Explain the purpose of the split ring commutator.
To reverse the current in the coil at every half rotation. This will reverse the induced force acting on the coil. This will maintain the direction of the moment on the coil. The coil will rotate in the same direction.
400
What are the 2 conditions for an object to be in static equilibrium?
Resultant force of all the forces acting on the object is 0N. Resultant moment of all forces about any point is 0Nm.
400
The specific heat capacity of a liquid is 2.8J/gK. The mass of the liquid is 5.0kg. A 500W heater is placed in the liquid. Find the time it takes to increase the temperature if the liquid by 5.0 deg C.
500 x t = 2800 x 5 x 5 t = 308s
400
A lens is used a magnifying glass. Describe the changes in the image when the observer moves slightly towards the lens on the opposite side of the lens.
No change.
400
An electric heater is connected to the power source in series with a thermistor in series. What is the disadvantage of this arrangement.
When temp. increases, R of thermistor decreases. The pd across thermistor decreases. The pd across electric heater increases. The power dissipated by the electric heater is higher when the temp. increases.
400
What is the purpose of the
To allow the induced current to flow to the external circuit and allows the coil to rotate but keeping the external circuit stationary.