Electric Field and Field Lines
The electric field is force per unit positive test charge, E = F/q, represented by field lines whose density indicates strength.
What is Electric Field and Field Lines?
The electric field is force per unit positive test charge, E = F/q, represented by field lines whose density indicates strength.
Key formula / rule: E = kQ/r2 for a point charge; field lines never intersect.
Key points
- Compute the resultant field due to a charge configuration.
- Analyse dipole behaviour in a uniform field.
Common exam trap
Drawing field lines that cross or start on negative charges.
Definitions
- Term
Electric Field and Field Lines
- Meaning
The electric field is force per unit positive test charge, E = F/q, represented by field lines whose density indicates strength.
- Term
Electric Field and Field Lines — explanation
- Meaning
The field concept removes the need to keep track of every source charge when studying a test charge. A dipole placed in a uniform field feels no net force but a torque pE sin t.
Learning objectives
Compute the resultant field due to a charge configuration.
Analyse dipole behaviour in a uniform field.
Formulae
- Key point
E = kQ/r2 for a point charge; field lines never intersect.
- Key point
Field inside a conductor in electrostatic equilibrium is zero.
- Key point
Dipole in a uniform field: torque = pE sin t, net force zero.
Prerequisites
PHY-U5-ELS-T1-S1-C1
Common mistakes
Drawing field lines that cross or start on negative charges.
Assuming a dipole experiences a net force in a uniform field.
Keywords
Electric
Field
Field
Lines
Practice preview
Which of the following statements about electric field lines is INCORRECT?…
easy
Two positive point charges of equal magnitude are placed some distance apart. Which of the following descriptions correctly represents the electric field lines?…
medium
A uniformly charged non-conducting ring of radius R has a total charge Q. What is the electric field magnitude at a point on its axis at a distance x from the center of the ring? (k is Coulomb's constant)…
hard