Title: InkPhysics / Electric fields
On every note of this deck, unless a note says otherwise:
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Front: RECALL
State how to find field strength from a potential-distance graph.
Back: E equals the magnitude of the gradient of the graph of V against r, and the field points down the potential gradient, from high potential to low.

Front: RECALL
State the field between parallel plates.
Back: A uniform field of strength E = V/d, with parallel, equally spaced field lines.

Front: RECALL
State the work done moving a charge along an equipotential.
Back: Zero, because the potential difference is zero.

Front: SPOT THE ERROR
Say what is wrong with this claim: A volt is an amount of energy.
Back: A volt is not an amount of energy; it is one joule per coulomb. The energy transferred depends on the charge moved as well: W = QV.

Front: RECALL
State the key difference between gravitational and electrostatic forces.
Back: Gravity only ever attracts, while the electrostatic force can attract or repel.

Front: SPOT THE ERROR
Say what is wrong with this claim: Field lines are the paths charges follow.
Back: Field lines show the direction of the force on a positive charge, not trajectories. A charge entering a uniform field at right angles follows a parabola, crossing the field lines.

Front: RECALL
Explain why the force ratio for two charged particles is independent of separation.
Back: Both forces follow an inverse-square law, so r^2 cancels in the ratio.

Front: DEFINITION
Define: Electric field strength.
Back: The force per unit charge on a small positive test charge placed in the field: E = F/Q, in N C^−1 or V m^−1.

Front: RECALL
State the angle between field lines and equipotential surfaces.
Back: They always cross at right angles.

Front: DEFINITION
Define: Coulomb's law.
Back: The force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation.

Front: DEFINITION
Define: Electric potential.
Back: The work done per unit positive charge to move a small test charge from infinity to that point.

Front: RECALL
State the energy transferred moving charge Q through pd ΔV.
Back: ΔW = QΔV.

Front: RECALL
Explain how a charged sphere is treated in Coulomb's law.
Back: A charged conducting sphere behaves as if all its charge were concentrated at its centre.

Front: RECALL
State the sign of electric potential in a radial field.
Back: Positive around a positive charge and negative around a negative charge, unlike gravitational potential, which is always negative.

Front: RECALL
State the path of a charge entering a uniform field at right angles.
Back: A parabola: constant velocity across the field and constant acceleration along it.

Front: SPOT THE ERROR
Say what is wrong with this claim: Gravity is the strongest force.
Back: Gravity is by far the weaker force: between two protons, electric repulsion exceeds gravitational attraction by about 10³⁶. Gravity dominates on large scales only because bulk matter is electrically neutral.