Electric Field Calculator
Calculate electric field strength from a point charge
How to Use
- Enter the magnitude of the charge
- Enter the distance from the charge
- Select the units for charge and distance
- Click calculate to see the electric field strength
- Review the force that would act on a test charge
What is an Electric Field?
An electric field is a physical field that surrounds electrically charged particles and exerts force on other charged particles within the field. It's a fundamental concept in electromagnetism that helps us understand how charges interact at a distance without direct contact.
The electric field is defined as the force per unit charge: E = F/q. It describes the strength and direction of the electric force that would be experienced by a test charge placed in the field.
Electric Field Formula
The electric field at a distance r from a point charge q is given by:
E = k × |q| / r²
Where:
- E = electric field strength (N/C or V/m)
- k = Coulomb's constant (8.99 × 10⁹ N⋅m²/C²)
- q = source charge (C)
- r = distance from the charge (m)
The electric field follows an inverse square law, meaning it decreases with the square of the distance from the charge.
Direction of Electric Field
The direction of the electric field depends on the sign of the source charge:
- Positive charge: Field points radially outward (away from the charge)
- Negative charge: Field points radially inward (toward the charge)
This means that a positive test charge would feel a repulsive force from a positive source charge (in the direction of the field) and an attractive force from a negative source charge (opposite to the field direction).
Electric Field Lines
Electric field lines are used to visualize electric fields. Key properties include:
- They begin on positive charges and end on negative charges
- The density of field lines represents field strength
- Field lines never cross
- They are tangent to the direction of the electric force on a positive test charge
Field lines provide intuitive visualization of how the electric field spreads out in space around charges.
Applications of Electric Fields
- Capacitors: Energy storage based on electric fields between plates
- Electron guns: Used in CRT monitors and X-ray devices
- Electrostatic precipitators: Air purification technology
- Van de Graaff generators: High-voltage generators using electric fields
- Particle accelerators: Using electric fields to accelerate charged particles
- Inkjet printers: Charging and deflecting ink droplets
- Touchscreens: Detecting finger position through electric field changes
Frequently Asked Questions
- What is the difference between electric field and electric force?
- The electric force (F) is the actual push or pull on a charge, measured in Newtons. The electric field (E) is the force per unit charge (E = F/q), measured in N/C. Electric field is a property of space that tells us what force a charge would experience there.
- Why does electric field follow an inverse square law?
- As you move away from a point charge, the electric field spreads out over an increasingly large area. Since the area of a sphere increases as the square of its radius (4πr²), the field strength decreases proportionally (1/r²).
- Can electric field exist in a vacuum?
- Yes! Electric fields can exist and propagate through vacuum. This is one of the fundamental discoveries of electromagnetism—charges interact through the electric field they create, not through direct contact.
- What does it mean when electric field strength is zero?
- When the electric field strength is zero at a point, no electric force would act on a test charge placed there. This typically happens at points between equal opposite charges, where their fields cancel out.
- How is electric field related to electric potential?
- The electric field is the gradient of electric potential: E = -dV/dr. In simple terms, the field points from high potential to low potential. The field strength tells you how quickly the potential changes with distance.