If a wire lies within a magnet field and an electric current is produced in the wire, what must be true about the magnetic field? A. the magnetic field must be produced by an electromagnet

B. the magnetic field must be produced by permanent magnets

C. the magnetic field cannot be moving

D. the magnetic field has to be moving

The rearrangement of particles in a physical change. hope this

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.