Download IB Physics III Review Sheet Unit 6B: Electromagnetism Students

IB Physics III
Review Sheet
Unit 6B: Electromagnetism
Students should be able to:
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explain that there are two types of charge (positive and negative) and use the movement of charges to
distinguish between electrical conductors and insulators (for example, in charging by induction)
state and explain the law of conservation of charge
describe the elementary charge (i.e. charge is quantized)
define electric field, electric potential, electric potential energy, potential difference
calculate the electric force between point charges, the electric field and electric potential due to a point
charge, and the electric potential energy of a system of point charges
determine the magnitude and direction of the force on a charged particle in an electric field
draw the electric field due to a point charge, two point charges (like or opposite charges), and parallel
plates of charge (including edge effects)
draw equipotential surfaces perpendicular to the electric field lines
determine the relative strength of an electric field based on the density of electric field lines or
equipotential surfaces
explain why electric field lines never cross one another (same for magnetic field lines)
interpret the negative gradient of a potential-versus-distance graph as the electric field strength at a point
in space (units: volts per meter)
correctly add electric force and electric field due to multiple point charges as vectors
determine the electric field strength between two parallel charged plates based on the potential
difference and separation distance between the plates (E = V/d), and vice versa
find the final speed of a charged particle accelerated from rest through a potential difference
define the electronvolt, a unit of energy (formal definition)
understand units (V = J/C for energy per unit charge, N/C or V/m as electric field strength)
state that moving charges give rise to magnetic fields
draw magnetic field patterns due to the current in a straight wire, a flat circular coil, and a solenoid
(straight and uniform through the center, wrapping around outside the ends)
determine the direction of the force on a current-carrying conductor in a magnetic field
define the ampere, the SI unit of current and one of the seven SI base units
determine the magnitude and direction of the force on a charge moving through a magnetic field
describe the motion of a charged particle moving at right angles to a magnetic field (circular)
describe the motion of a charged particle moving at an oblique angle to a magnetic field (helical)
explain the differences between charged particles acted on by electric and magnetic fields (for example,
in terms of work done by the electric or magnetic force)
solve problems involving the movement of a charged particle between parallel plates, with and without
crossed fields (i.e. with and without a magnetic field in addition to the electric field)
Since Wilson asked about equations for magnetic field strength (flux density) due to the current in a wire, here is
the equation for the magnetic flux density B a distance r from a wire carrying a current I:
If a solenoid contains N loops of wire wrapped along an axial length L with a density of n = N/L turns per unit
length, the magnetic field inside the solenoid is approximately uniform with flux density
Note that the magnetic field strength (flux density) produced by a current in either case is directly proportional
to the current I. In the case of a straight wire it decreases the further you get from the wire (being inversely
proportional to r), but inside an ideal solenoid it is uniform.