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Electric dipole
Intermediate
Two equal and opposite charges separated by d.
p = qdTwo equal and opposite charges ±q separated by d form a dipole with moment p = qd (from − to +). Water molecules are dipoles.
p = 1.6×10⁻¹⁹ × 10⁻¹⁰ = 1.6×10⁻²⁹ C·m.
Net charge is zero but there's still a field.
In more detail
An electric dipole is a pair of equal and opposite charges separated by a small distance. The dipole moment p = qd points from the negative to the positive charge.
Real-world uses
- Water molecules are polar dipoles, which explains their solvent properties.
- Antennas act as dipoles to radiate radio waves.
- Water molecules are electric dipoles, which is why water is a good solvent for salts and why it sticks to glass.
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Frequently asked questions
Is the net charge of a dipole zero?
Yes, but its field is not zero, because the two charges are separated.
What is the unit of dipole moment?
Coulomb metres.
What makes a dipole?
Two equal and opposite charges separated by a small distance. The pair has no net charge, but its separated charges still produce a field.
Related topics in Electrostatics
Electric field · Field of a point charge · Electric field lines · Field of a dipole · Torque on a dipole in a field · Potential energy of a dipole