Question

Electrical as well as gravitational effects can be thought to be caused by fields. Which of the following is true for an electrical and gravitational field ?

• A. Fields are useful for understanding forces acting through a distance.
• B. The field concept is often used to describe contact forces.
• C. There is no way to verify the existence of the force field since it is just a concept.
• D. Gravitational or electrical field does not exist in the space around an object.

Answer 1

The Correct Option is A

Answer: The correct statement is: (A) Fields are useful for understanding forces acting through a distance.

Explanation:

Fields are an essential concept in physics that help describe how forces can act through a distance without direct contact. There are two primary types of fields that describe forces acting at a distance:

• Electric fields: These are created by electric charges and describe the force that a charge exerts on other charges in its vicinity.
• Gravitational fields: These are created by masses and describe the force that a mass exerts on other masses in its vicinity.

Both fields act through space and influence other objects within their reach, which is why we can observe forces at a distance, such as gravitational attraction between planets or the electric force between charged particles.

Therefore, the correct answer is: (A) Fields are useful for understanding forces acting through a distance. 

Answer 2

Let's analyze each statement regarding electric and gravitational fields:

1. Fields are useful for understanding forces acting through a distance.
   Both gravitational force (between masses) and electrical force (between charges) are examples of "action at a distance" forces. The field concept was developed precisely to explain how these forces can be exerted across empty space without physical contact. A mass creates a gravitational field in the space around it, and another mass placed in this field experiences a force. Similarly, a charge creates an electric field, and another charge in that field experiences a force. The field acts as an intermediary. This statement is true.
2. The field concept is often used to describe contact forces.
   Contact forces, like the normal force or friction, arise from complex electromagnetic interactions at the microscopic level between the surfaces in contact. While ultimately based on fundamental fields (electromagnetic), the macroscopic description of contact forces generally doesn't rely on the field concept in the same way as gravitational or electrostatic forces acting at a distance. The field concept is primarily associated with non-contact, action-at-a-distance forces. This statement is generally false.
3. There is no way to verify the existence of the force field since it is just a concept.
   While a field is a conceptual tool, its existence is inferred and verified through its measurable effects. We can detect and measure an electric field by observing the force it exerts on a test charge (\( \vec{F} = q\vec{E} \)). We can detect and measure a gravitational field by observing the force it exerts on a test mass (\( \vec{F} = m\vec{g} \)). Experiments like mapping field lines or observing the acceleration of objects provide verification of the field's effects, and thus support the utility and physical relevance of the field concept. This statement is false.
4. Gravitational or electrical field does not exist in the space around an object.
   This statement contradicts the very definition of a field. A field is a property of space itself, created by the presence of a source (mass or charge). The gravitational field exists in the space surrounding a mass, and the electric field exists in the space surrounding a charge. It is this field that mediates the force on other objects placed in that space. This statement is false.

Therefore, the only true statement is that fields are useful for understanding forces acting through a distance.