Fields Flashcards
(30 cards)
What is a non-contact force and what are examples of fields that cause them?
A non-contact force occurs when objects experience a force without touching, due to being in a field. Examples: gravitational and electric fields.
How do gravitational and electric fields differ?
Gravitational fields affect all objects with mass; electric fields affect only charged objects.
What is the unit and value of gravitational field strength on Earth?
Unit: N/kg. On Earth: 9.81 N/kg.
How do gravitational field lines behave around Earth?
They diverge from the center; closer lines mean a stronger field. It’s a radial field.
What defines a uniform field?
Field lines are parallel, and field strength is constant throughout.
What direction do electric field lines point?
Always in the direction a positive test charge would move.
What is the equation for gravitational field strength in a radial field?
g ∝ M/r²
What constant is used in Newton’s law of gravitation and what is its value?
Gravitational constant G = 6.67 × 10⁻¹¹
What is the electric field strength constant and its shortcut value?
1/(4πε₀) = 8.99 × 10⁹, shortcut: k = 9 × 10⁹
How does gravitational field strength vary inside a planet?
It decreases linearly to zero at the center. g ∝ ρR if density ρ is constant.
What is Newton’s Law of Gravitation?
F = G(m₁m₂/r²). Force is proportional to the product of masses and inversely proportional to the square of their separation.
What is Coulomb’s Law?
F = k(q₁q₂/r²). Force is proportional to the product of charges and inversely proportional to the square of their separation.
How do you calculate force from a field?
Gravitational: F = mg; Electric: F = Eq
What is the equation for gravitational potential energy?
U = -GMm/r, only valid in non-uniform fields.
What is gravitational potential (V) and its units?
Work done per unit mass to move from infinity to a point. Unit: J/kg.
What is electric potential and how is it defined?
Work done per unit positive charge from infinity to a point. Unit: J/C (Volts).
What is the formula for gravitational and electric potential?
Gravitational: V = -GM/r; Electric: V = kQ/r
What are equipotentials and their relationship with field lines?
Lines of constant potential; always perpendicular to field lines.
What does the gradient of a potential-distance graph represent?
Field strength at that point (potential gradient).
How is potential energy change calculated from a potential graph?
ΔPE = mΔV for gravity or qΔV for electric fields.
What is the speed of a satellite in orbit?
v = √(GM/r)
What is Kepler’s Third Law?
T² ∝ r³. Orbital period squared is proportional to orbital radius cubed.
What is escape velocity?
v = √(2GM/r). It’s the speed needed to escape a planet’s gravity.
What is the relationship between escape velocity and potential?
v_escape = √(2V), where V is gravitational potential.
