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

Options

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

Answer

To determine which statement is true regarding electrical or gravitational fields, we can analyze the given options step by step.

### Step 1: Understand the Concept of Fields
Electrical and gravitational fields are concepts used to describe the influence that a charged or massive object exerts on other objects in their vicinity. These fields allow us to understand how forces act at a distance without the need for direct contact.

### Step 2: Analyze Each Option
1. **Option A**: "The field concept is often used to describe contact forces."
- This statement is incorrect. Fields are used to describe non-contact forces (like gravitational and electric forces), not contact forces.

2. **Option B**: "Gravitational or electric field doesn't exist in the space around an object."
- This statement is also incorrect. Both gravitational and electric fields exist in the space around objects that have mass or charge.

3. **Option C**: "Fields are useful for understanding forces acting through a distance."
- This statement is correct. Fields help us understand how forces can act over a distance without direct contact, such as the gravitational force between two masses or the electric force between two charges.

4. **Option D**: "There is no way to verify the existence of a force field since it is just a concept."
- This statement is misleading. While fields are conceptual, their effects can be measured and verified through experiments.

### Step 3: Conclusion
After analyzing all the options, we find that **Option C** is the correct answer. Fields are indeed useful for understanding forces acting through a distance.

### Final Answer
**C. Fields are useful for understanding forces acting through a distance.**