Answer:
I see no eaquations?
It should be matter=constant
Answer:
t = 4 seconds
Explanation:
The question is "The intensity of current flowing through a conductor is 2μA. How long will it take 5x1013 electrons to cross a certain cross section of the conductor?
"
Current, 
No of electrons, 
We need to find how long will it take to given no of electrons to cross a certain cross section of the conductor.
Electric current,

t is time
Also, q = ne

So, it will take 4 seconds.
Answer:
B. They show the pattern made by the magnetic field lines around the
magnets
Explanation:
Using iron fillings, the pattern of the magnetic field lines around a bar magnet can be known.
Magnetic field lines are the line of force around a bar magnet.
- These iron fillings will trace the pattern of the magnetic field around the magnet.
- The domains of the iron fillings begins to align and orient with that of the prevailing magnetic field around.
- Those areas with the strongest force will attract more fillings and those far away will attract lesser fillings.
Answer: force of gravity on the body due to height difference above the earth's surface
Explanation: as you increase the height of a body above ground, you do work against gravity in moving it from a point on the earth's surface to that point. So a body falling has a stored up gravito-potential energy which acts on it downward due to its mass, accelerating it downwards
Answer b): kinetic energy of the body
Explanation: the downward force produces an acceleration of magnitude 9.81m/s2 downwards which means an increasing velocity. This increasing velocity means the kinetic energy of the body is increasing (kinetic energy is proportional to velocity of the body squared)