A2 Unit 18 Electric Fields

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Define electric field

Region of space in which any object with charge will experience a force

Give the equation for Coulomb’s Law

F = q1q2 / 4π𝜀0r²

Define electric field strength

Force per unit charge

Give the unit of electric field strength

NC⁻1

Give the field strength for a radial electric field at a distance r from a point charge Q

E = Q / 4π𝜀0r²

Give the properties of a uniform electric field

Field strength and direction are the same at every point

Give the equation for the magnitude of the electric field strength at any point in a uniform field

E = V/d

What kind of trajectory will a charged particle entering a uniform field in a direction initially perpendicular to the field have?

Parabolic trajectory

Define electric potential

Work done per unit charge to bring a small positive test charge from infinity to that point

Give the equation for the magnitude of the absolute electric potential at any point in a radial field caused by a point charge

V = Q / 4π𝜀0r

Define electric potential difference

Difference between the electric potential at two points in an electric field

Give the formula for the work done in moving a charge between two points in a electric field

ΔW = QΔV

Define an equipotential surface in an electric field

Surface where the electric potential is the same at all points

What is the relationship between electric field strength and potential difference?

E = ΔV/Δr

How can the electric field strength at any point in an electric field be found from a graph of V against r?

Gradient of the graph at that point

Give the equation for the potential energy of two point charges

E_e = q1q2 / 4π𝜀0r