Electric Field and Field Lines - UNSOLVED PRACTICE SET
Chapter: Electric Charges and Fields | Topic: Electric Field and Field Lines
ELECTRIC FIELD AND FIELD LINES - UNSOLVED PRACTICE SET
Topic: Electric Field and Field Lines
Multiple Choice Questions
Q1. The electric field at a point is defined as:
- Force per unit charge experienced by a small positive test charge placed at that point
- Force experienced by any charge placed at that point
- Potential energy per unit charge
- Work done in moving a unit charge to that point
Q2. The SI unit of electric field intensity is:
- N/C
- V/m
- Both (a) and (b)
- J/C
Q3. Electric field lines around a negative point charge are:
- Radially outward
- Radially inward
- Concentric circles
- Parallel to each other
Q4. The density of electric field lines in a region indicates:
- The direction of the field
- The magnitude of the electric field
- The potential at that point
- The charge present in the region
Q5. Electric field lines never intersect because:
- They are parallel to each other
- At any point, the electric field can have only one direction
- They originate from negative charges
- They terminate at positive charges
Q6. A uniform electric field is represented by field lines that are:
- Converging
- Diverging
- Parallel and equally spaced
- Curved
Short Answer Questions
Q7. Define electric field intensity. Why is a test charge taken to be positive and very small?
Q8. Draw the pattern of electric field lines around
(a) a single positive point charge, and
(b) an electric dipole.
Q9. Why do electric field lines not form closed loops? Explain with reference to the nature of electric charges.
Q10. The electric field lines are closer together near a charged object and farther apart at greater distances. What does this tell you about the electric field strength?
Q11. A student draws electric field lines around two positive charges placed close to each other. Describe what the pattern looks like and explain why.
Q12. What is the electric field inside a uniformly charged hollow sphere? Explain your answer.
Long Answer Questions
Q13. Derive the expression for the electric field intensity at a distance r from a point charge Q. Draw the diagram showing the direction of the field for both positive and negative charges.
Q14. Explain the properties of electric field lines with suitable diagrams. Why can't two electric field lines intersect each other? What would happen if they did?
Q15. Two point charges +4 μC and −4 μC are placed 20 cm apart.
(a) Calculate the electric field at the midpoint between the two charges.
(b) Draw the electric field lines in the region around these charges.
(c) At what point on the line joining the charges is the electric field zero?
[Given: k = 9 × 10⁹ N m² C⁻²]
Numerical / Application-Based Problems
Q16. A point charge Q = +5 μC is placed at the origin in vacuum.
(a) Calculate the electric field intensity at a point P located 30 cm from the charge along the x-axis.
(b) Find the force experienced by a test charge q = +2 μC placed at point P.
(c) If the point P is moved to a distance of 60 cm, by what factor does the electric field change?
[Given: k = 9 × 10⁹ N m² C⁻²]
Q17. Two point charges q₁ = +6 μC and q₂ = −2 μC are placed on the x-axis at x = 0 and x = 40 cm respectively.
(a) Calculate the electric field at x = 20 cm (midpoint).
(b) Find the point on the x-axis where the electric field is zero.
(c) Calculate the electric field at a point on the y-axis at y = 30 cm.
[Given: k = 9 × 10⁹ N m² C⁻²]
Q18. In a physics demonstration, a teacher places two identical metal plates parallel to each other, creating a uniform electric field of 500 N/C between them. A tiny charged dust particle of mass 2 × 10⁻⁶ kg and charge +4 nC is placed in the field.
(a) Calculate the electric force on the dust particle.
(b) What is the acceleration of the particle?
(c) If the particle starts from rest, how far will it travel in 2 seconds? (Ignore gravity)