D. Fields
Start with Concept to understand a topic, then use Question Bank to check what you know.
Your progress
Sign in to see your mastery and mistakes.
D.1 Gravitational fields
D.1.1—Kepler’s three laws of orbital motion
• Kepler’s three laws of orbital motion.
D.1.2—Universal gravitation
• Universal gravitation: F=Gm1m2/r^2 for point masses.
D.1.3—Point-mass approximation
• Extended bodies can be treated as point masses only under suitable conditions.
D.1.4—Gravitational field strength
• Gravitational field strength: g=F/m=GM/r^2.
D.1.5—Gravitational field lines
• Gravitational field lines.
D.2 Electric and magnetic fields
• Direction of forces between the two types of electric charge.
• Coulomb’s law: F=kq1q2/r^2 for point charges; k=1/(4πε0).
• Conservation of electric charge.
• Millikan’s experiment as evidence for quantization of electric charge.
• Charge transfers by friction, electrostatic induction or contact. • Grounding can remove or add charge.
• Electric field strength: E=F/q.
• Electric field lines.
• Relationship between field line density and field strength. • Greater field-line density indicates stronger field.
• Uniform field between plates: E=V/d.
• Magnetic field lines.
D.3 Motion in electromagnetic fields
• Motion of a charged particle in a uniform electric field.
• Motion of a charged particle in a uniform magnetic field.
• Charged particles can move in perpendicular uniform electric and magnetic fields.
• Magnetic force on moving charge: F=qvB sinθ.
• Force on current-carrying conductor: F=BIL sinθ.
• Force per unit length between parallel wires: F/L=μ0I1I2/(2πr). • Parallel currents attract when currents flow in the same direction.