Because gases flow easily. A hot batch of gas can rise through
the surrounding gas a lot easier than, say, a hot batch of mud can
rise through the surrounding mud.
It really depends on what the bulb is being used for, since efficiency means how much of the output is USEFUL.
If the bulb is being used for light in a dark room, then it produces (8.2% x 21W) = 1.72 joules per second of light energy.
If the bulb is being used to keep a hamster cage or a fish tank warm, then the 8.2% is the useful part, and the light is the other (91.8% x 21W) = 19.28 joules per second.
<span>Right-hand rule reveals a connection between the current and the magnetic field lines in the magnetic field. It is also called Ampere`s right hand screw rule. It determines the direction of the magnetic field surrounding a current carrying wire. The thunb points direction of current and fingers point the direction of magnetic lines of force. Answer: C ) a counterclockwise rotation.</span>
Answer: Heating from the crust and mantle.
Explanation: Tremendous heat and pressure within the earth cause the hot magma to flow in convection currents. These currents cause the movement of the tectonic plates that make up the earth's crust.
Resistance of a wire is directly proportional to its length and inversely proportional to the square of its radius.
Thus, if the length is doubled, and the radius is halved:
R₂ = 2R₁/(1/2)²
R₂ = 8R₁
Therefore the resistance increases eight times.