All electric circuits have devices that are run by _____ energy.
1 answer:
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Answer:
1) from the positive x-axis.
2)
Explanation:
Given:
speed of rowing in still water,
1)
speed of water stream,
we know that the direction of resultant of the two vectors is given by:
where:
the angle of resultant vector from the positive x-axis.
angle between the given vectors
When the rower wants to reach at the opposite end then:
so,
from the positive x-axis.
2)
Now the resultant velocity of rowing in the stream:
Therefore time taken to cross a 4 miles wide river:
Answer:
-75.35°
Explanation:
Let C be the sum of the two vectors A and B. Hence, we can write the following
but since the vector C is in the -y direction, = 0 and
= —12 m.
Thus
similarly, we can determine by rearranging equation (1)
so the magnitude of B is
Finally, the direction of B can be calculated as follows
Ф=
hence the vector B makes an angle of 75.35 clockwise with + x axis
1. False
Explanation: it's exactly the opposite. In fact, Lenz's law states that the induced current and the induced emf in a conductor are generated in such a direction that opposes to the change in magnetic flux through the coil. This is summarized by the negative sign in the Faraday's Newmann Lenz law:
where is the emf induced and
is the rate of change of magnetic flux through the coil.
Lenz's law is a consequence of the law of conservation of energy. In fact, we have:
- If the magnetic flux through a coil is increasing, then the induced current has a direction such that the magnetic field generated by the coil is opposite to the direction of the external magnetic field, in order to decrease the total flux
- If the magnetic flux through a coil is decreasing, then the induced current has a direction such that the magnetic field generated by the coil is in the same direction as the external field, in order to increase the total flux
2. False
Explanation: the magnetic flux through a surface is given by
where
B is the magnitude of the magnetic field
A is the surface area
is the angle between the direction of B and the normal vector to the surface
As we see, the magnetic flux depends not only on B and A, but also on the orientation of the coil with respect to the magnetic field.
3. False
Explanation:
- Sound waves are mechanical waves: mechanical waves are waves consisting of oscillations of the particles in a medium. Due to their nature, therefore, mechanical waves can propagate only in the presence of a medium
- Electromagnetic waves are NOT mechanical waves: they consist of oscillations of electric and magnetic fields, in a direction perpendicular to the direction of propagation of the wave. Since em waves are not mechanical waves, they do NOT need a medium to propagate, since they can also travel through a vacuum; therefore the original statement is false.