Question

1

Write a few sentences addressing each of these prompts.

1. In your own words, what is the difference between electric force, electric field, and electric charge? You may find it easier to describe how the three concepts are related.

2. If two charges are observed to repel one another, what can you say about the sign of each? What if the two attract one another? With only this information (whether they attract or repel) can you identify which charge is which type (positive or negative)? What does this mean about the assignment of “positive” or “negative” charge?

3. In a very contrived situation, two students are discussing the following problem.

   “A point charge of 2 μC is placed in an electric field and experiences a force of 27 N. Find the electric field. The 2 μC charge is removed and replaced with a 4 μC charge. What is the electric field now?”

   One student insists the field is 13.5 N/C in both cases and the other says it is 13.5 N/C in the first case and 6.75 N/C in the second case. Why might each student take their stated position and which one is correct? Provide an argument based on the physics that could help the incorrect student see their error.

Answer 1

The electric charge is the physical properties of matter due to which it experience electrostatic force (either attractive or repulsive) in the presence of other object having same type of physical property.

We know that when an object have charge then it exerts force on other charged object in the space around it and this force is known as electric force .

Nowadays , it is assumed that force between two charges is a two step process . First of all , a charge creates a field around it and when another charge comes into this field , then field exerts force on it . When we calculate strength of electric field , then it is called electric intensity .

When two charges repel each other then it can be said that they are of same nature i.e having same sign we can not predict whether both charges are either positive or negative.  if they attract each other then it can be said they are of opposite nature .i.e having opposite sign but we can not which one is positive and which one is negative . By attraction and repulsion among charged bodies it can be clearly said that there are two types of charges that exist in nature . AND by convention one of them is called as positive and other negative .

Here, it is said that the charge 2 is placed in an electric field which is due to some other configuration of charges.

The force experienced by the charge is 27 Newton. From definition of electric field we know that , the force experienced by a unit positive charge gives electric field at a point .

2 experiences 27 newton.

1 C will experience =   =   Newton/Coulomb = Electric field

instead of 2 if 4 is present then it will have no effect on electric field at that point because electric field is due to some other configuration of charges .Also the electric field due to a charge particle at that point is zero .

Both the students are incorrect as electric field = Newton/Coulomb