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- A small electric immersion heater is used to heat 68 g of water for a cup of instant coffee. The heater is labeled “76 watts” (it converts electrical energy to thermal energy at this rate). Calculate the time required to bring all this water from 23°C to 100°C, ignoring any heat losses. (The specific heat of water is 4186 J/kg·K.)
- A vertical glass tube of length L = 1.3m is half filled with a liquid at 15.8 ˚C. How much will the height of the liquid column change when the tube is heated to 34.0 ˚C? Take αglass = 1.25× 10-5/K and βliquid = 4.46× 10-5/K.
The boiler operates on a Carnot heat pump, which is installed between a boiler in which the water is at 60 ° C and a basement in which it is 10 ° C.
(a) What is the efficiency of the heat pump?
(b) The pump heats water with a power of 1 kW. How much electrical power does the pump consume?
(c) When pouring water from a boiler with some flow, cold tap water flows into it. Indicate how you would come to a connection during the maximum flow at which this boiler is still "catching up" by continuously heating the supply water, and during the cold water temperature. If possible, complete this connection and state the meaning of all symbolic quantities used
Assume that lightning strikes completely vertically and that a known current flows from the cloud into the ground for some time. We want to detect a lightning strike with the help of a coil that is connected directly to a voltmeter. Explain which phenomenon is responsible for lightning detection. Sketch the magnetic field of lightning and how the coil should be oriented for the effect to be strongest.
The plate capacitor is already charged with some charge and disconnected to keep the charge on it. What changes increase the voltage across the capacitor?
• Increase the surface area of the plates
• Reduce the surface area of the plates
• Increase the distance between the plates
• Reduce the distance between the plates
• Insert a dielectric between the plates
One-meter-long coaxial cable is incorrectly connected to the output device, so part of the signal bounces back on the connection. Determines the speed of the signal along the wire if we see echoes in the signal with a delay of 10 ns.
The volume of 2.4 m3 of an ideal gas initially at 0C and pressure 1.013 x 105 Pa is compressed to 1.6 m3 and its temperature remains the same. Calculate the new pressure
A machine has an effiency of 75% the work done when the machine is used to raise a load of 50kg through a vertical distance of 6m is
An object volume 4m is totally immersed in a liquid of density 1030kgm. Calculate the upthrust of liquid on the object. A body has mass 10kg in air and 4kg when immersed totally in water. Calculate the volume of the body and its density.
A particular species of plant grows 3.7 m in 14 days. What is it's growth rate in micrometers per seconds
A 180 g mass on a smooth surface is attached to a horizontal spring with a spring constant 8 N m-1. The mass is set to oscillate by pulling it 5.0 cm from its equilibrium position and released.
a) Calculate the period of the oscillation.
[ 1 mark ]
b) Calculate the maximum speed of the mass.
[ 2 marks ]
c) Calculate the maximum acceleration of the mass
[ 2 marks ]
