1.) Self inductance is a physical quantity that depends only on the geometry of
ID: 306347 • Letter: 1
Question
1.) Self inductance is a physical quantity that depends only on the geometry of the inductor. A solenoid with N loops, length l, and cross-sectional area A, with current I flowing through the loops, is an inductor. Which of the following actions will reduce the self inductance of a solenoid?
A.) Increasing the cross-sectional area A of the solenoid.
B.) Increasing the number of loops N of the solenoid.
C.) Increasing the current I through the solenoid.
D.) Increasing the length l of the solenoid.
2.) Heinrich Hertz showed that the radio waves created in his experiments and visible light were two examples of the same phenomenon, known as electromagnetic waves. He did this by showing his radio waves traveled at the same speed as visible light. How then do radio waves differ from visible light (for example, why can't we see radio waves, when we can see visible light?)
A.) We can create a source of radio waves, but we cannot create a source of visible light.
B.) A radio wave is a spherical wave, while visible light is a plane wave.
C.) Radio waves and visible light travel at different speeds.
D.) We can build machines that detect radio waves, but we cannot build a machine that detects visible light.
E.) We can build machines that detect visible light, but we cannot build a machine that detects radio waves.
F.) Radio waves and visible light have different frequencies.
3.) Intensity of an electromagnetic wave has units
A.) energy per area [ in SI units: J/m2 ] energy [in SI units: J ]
B.) energy per time per length [ in SI units: J/(s m) ]
C.) energy per time per area [ in SI units: J/(s m2) ]
D.) energy per length [ in SI units: J/m ]
E.) energy per time [ in SI units: J/s ]
4.) As an electromagnetic wave propagates, it transports
A.) momentum, but no energy.
B.) both energy and momentum.
C.) energy, but no momentum.
D.) neither energy nor momentum.
Explanation / Answer
1. Self inductance of a solenoid is directly proportional to number of turns N, area of the coil A, and inversely proportional to the length. Hence if the length of the solenoid is increased then the self inductance of the solenoid will reduce. hence Option D is correct.
2. All waves of the electromagnetic have different frequencies. Hence the radio waves and the visible light have the different frequency. Option C is correct.
3. Intensity has the formula of energy per unit time per unit area. Hence option C is correct.
4. Electromagnetic waves transport both energy and momentum through space by photons. Option B is correct.
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