Downstream, the current is helping the swimmer go faster relative to the land
Answer:
Maximum charge will be 
Explanation:
We have given force ion the moving charge 
Maximum speed of the moving charge v = 30 m /sec
Magnetic field 
We have to fond the charge
Force on moving charge is given by
So 
Maximum charge will be
Answer: Moon is much smaller in size and has very less mass, when compared to our mighty earth and there is absence of strong magnetic field on the moon which could protect from the incoming solar radiation from the sun. Since there is no magnetic field, it can swipe off any materials that are present there on the moon, diminishing the atmosphere.
This is the reason why moon does not have any atmosphere.
