Hello, some examples are Earth science, chemistry and Navigation science (don't know if there is called in this way).
In Earth Science we can talk about Geomagnetism.
In Chemistry, electrostatics and electrochemistry.
In Navigation science the compass.
Hope it helped.
Answer:
a. 
b. 
Explanation:
Given:



The runner force average to find given the equations
a.




b.
Work done by the system by this force so





Answer:
The polarity of electromagnet also gets reversed when the direction of current is reversed. The current flows from negative terminal to positive terminal in an electromagnet due to the flow of electrons so polarity is also established in the electromagnet. As, the current direction is reversed, the polarity of magnet also gets reversed because the polarity of magnet depends on the direction of the current.