Answer:
Motors commonly contain a "commutator" which allows a magnetic field due to a loop of wire to always be in a say "clockwise or counterclockwise" direction even tho the loop of wire is rotating.
That means that magnetic field due to the surrounding magnets is always in the same direction, but the magnetic field due to the rotating loop of wire is continually changing so that it will always oppose the surrounding field which remains in a constant direction.
This is most easily seen in a "DC - direct current motor".
Answer:
450N
Explanation:
Given data
Mass m= 75kg
Acceleration= 6m/s^2
From the Newtons first law, F=ma
substitute
F=75*6
F= 450N
Hence the force is 450N
Burning of gases is one the example of chemical change
Answer:
Increase by a factor of 4.
Explanation:
The acceleration of a car moving with speed v in a circle of radius R is given by:
Now if we double the speed 
in the equation above, it becomes 
. Thus:
Therefore the acceleration is increased by a factor of 4.
Answer:
1-In a uniform electric field, the field lines are straight, parallel, and uniformly spaced this statement is true.
2-Electric field lines near positive point charges radiate outward. this statement is also true.
3-The electric force acting on a point charge is proportional to the magnitude of the point charge. this statement is true as well.
Explanation:
the electric field created by a point charge is defined by E=KQ/r^2 where k is constant, q is magnitude of charge and r is the distance away from the point charge so the electric filed is distance dependent and can not be constant at all distances.
electric field lines near a negative point charge are directed radially inward because negative charge attracts the field and is not clockwise.
