Physics Formula Electric Field Strength

Physics Formula for Electric Field Strength

Electric field strength is a fundamental concept in electromagnetism that describes the force per unit charge exerted on a test charge in the presence of an electric field. The electric field strength, denoted as E, is defined by the following formula:

1. Electric Field Strength Formula

The formula for electric field strength is:

E = F / q

Where:

E = Electric field strength (N/C or V/m)
F = Force exerted on the charge (Newtons)
q = Charge (Coulombs)

Explanation

The electric field strength represents the force experienced by a small positive test charge placed in the field. The stronger the electric field, the greater the force on the charge. The unit of electric field strength is either Newtons per Coulomb (N/C) or Volts per meter (V/m).

2. Example 1: Electric Field Strength Around a Point Charge

Let's calculate the electric field strength created by a point charge.

Suppose we have a point charge Q = 2 × 10^-6 C (2 microcoulombs) and we want to find the electric field strength at a distance r = 0.5 m from the charge.

Solution:

The electric field strength due to a point charge is given by:

E = k × |Q| / r²

Where:

k = Coulomb's constant = 9 × 10⁹ N·m²/C²
Q = Charge (Coulombs)
r = Distance from the charge (meters)

Substituting the values:

E = (9 × 10⁹ N·m²/C²) × (2 × 10^-6 C) / (0.5 m)²

E = (9 × 10⁹) × (2 × 10^-6) / (0.25)

E = (18 × 10³) / 0.25 = 72,000 N/C

The electric field strength is 72,000 N/C.

3. Relationship Between Electric Field and Voltage

Another important relationship in electromagnetism is the connection between electric field strength and voltage (V). The electric field strength can also be expressed as:

E = V / d

Where:

V = Voltage (Volts)
d = Distance between the plates or points (meters)

Example 2: Electric Field Between Parallel Plates

Suppose we have two parallel plates with a voltage of 500 V applied across them, and the distance between the plates is 0.02 m. The electric field strength can be calculated as:

E = V / d

Substituting the values:

E = 500 V / 0.02 m

E = 25,000 V/m

The electric field strength between the plates is 25,000 V/m.

4. Importance of Electric Field Strength

Electric field strength is a critical concept in many areas of physics and engineering. It helps in understanding how charged particles behave in different fields, from designing electronic components to studying natural phenomena such as lightning. A strong electric field can result in high forces on charges, which can lead to practical applications like electric motors, capacitors, and generators.

Conclusion

The formula for electric field strength is essential for understanding how forces act on charges in an electric field. Whether you're calculating the field around a point charge or between parallel plates, the ability to determine electric field strength is fundamental to solving various problems in physics.