Answer:

Explanation:
For a charge moving perpendicularly to a magnetic field, the force experienced by the charge is given by:

where
q is the magnitude of the charge
v is the velocity
B is the magnetic field strength
In this problem,



So the force experienced by the electrons is

Answer:
The current needed to transmit Power of 4 W is 28.47 A
Solution:
As per the question:
Length of the antenna, 
Frequency, 
Power transmitted, 
Now,
For a monopole antenna:

where
= wavelength transmitted by the antenna
c = speed of light in vacuum

Now,
Since, the value of
>>
thus the monopole is a Hertian monopole.
The resistance is calculated as:




Now, the current I is given by:

Answer:
Current, I = 1000 A
Explanation:
It is given that,
Length of the copper wire, l = 7300 m
Resistance of copper line, R = 10 ohms
Magnetic field, B = 0.1 T

Resistivity, 
We need to find the current flowing the copper wire. Firstly, we need to find the radius of he power line using physical dimensions as :




r = 0.00199 m
or

The magnetic field on a current carrying wire is given by :



I = 1000 A
So, the current of 1000 A is flowing through the copper wire. Hence, this is the required solution.
The work done on the wagon is 3549 J
Explanation:
The work done by a force when moving an object is given by
where
:
F is the magnitude of the force
d is the displacement
is the angle between the direction of the force and of the displacement
In this problem we have the following data:
F = 87 N is the magnitude of the force
d = 44 m is the displacement of the wagon
is the angle between the direction of the force and the displacement
Substituting, we find the work done

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Because of gravity and friction.